Methods of preparing anodes using tin as active material

ABSTRACT

Improved anodes and cells are provided, which enable fast charging rates with enhanced safety due to much reduced probability of metallization of lithium on the anode, preventing dendrite growth and related risks of fire or explosion. Anodes and/or electrolytes have buffering zones for partly reducing and gradually introducing lithium ions into the anode for lithiation, to prevent lithium ion accumulation at the anode electrolyte interface and consequent metallization and dendrite growth. Various anode active materials and combinations, modifications through nanoparticles and a range of coatings which implement the improved anodes are provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/480,904, filed on Apr. 6, 2017, which is a continuation-in-part ofU.S. patent application Ser. No. 15/414,655, filed Jan. 25, 2017 and acontinuation-in-part of U.S. patent application Ser. No. 15/447,889,filed Mar. 2, 2017 and a continuation-in-part of U.S. patent applicationSer. No. 15/447,784, filed Mar. 2, 2017; U.S. patent application Ser.Nos. 15/480,904 and 15/447,784 further claim the benefit of U.S.Provisional Patent Application Nos. 62/319,341, filed Apr. 7, 2016,62/337,416, filed May 17, 2016, 62/371,874, filed Aug. 8, 2016,62/401,214, filed Sep. 29, 2016, 62/401,635, filed Sep. 29, 2016,62/421,290, filed Nov. 13, 2016, 62/426,625, filed Nov. 28, 2016,62/427,856, filed Nov. 30, 2016, 62/435,783, filed Dec. 18, 2016,62/441,458, filed Jan. 2, 2017; U.S. patent application Ser. No.15/480,904 further claims the benefit of U.S. Provisional PatentApplication Nos. 62/481,752, filed Apr. 5, 2017 and 62/482,227, filedApr. 6, 2017; U.S. patent application Ser. No. 15/447,889 further claimsthe benefit of U.S. Provisional Patent Application Nos. 62/435,783,filed Dec. 18, 2016, 62/441,458, filed Jan. 2, 2017, all of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to the field of energy storage devices,and more particularly, to fast charging lithium ion batteries.

2. Discussion of Related Art

A major barrier in battery technology concerns safety requirements,particularly when batteries are overheated or overcharged, resulting inthermal runaway, cell breakdown and possibly fire or explosion.Additionally, a short circuit or a design defect may also bring aboutbattery failure resulting in fire and safety risks. Lithium ionbatteries in particular, while having operational advantages, arepotentially flammable due to their high reactivity, particular when incontact with humidity.

SUMMARY OF THE INVENTION

The following is a simplified summary providing an initial understandingof the invention. The summary does not necessarily identify key elementsnor limit the scope of the invention, but merely serves as anintroduction to the following description.

One aspect of the present invention provides an anode comprising anodeactive material particles, wherein the anode active material particleshave, at a surface thereof, a buffering zone configured to receivelithium ions from an interface of the anode active material particleswith an electrolyte, partly mask a positive charge of the receivedlithium ions, and enable the partly masked lithium ions to move into aninner zone of the anode active material particles for lithiationtherein, wherein the buffering zone comprises a plurality of electrondonating groups interspaced between non-electron donating groups at aratio of at least 1:2.

These, additional, and/or other aspects and/or advantages of the presentinvention are set forth in the detailed description which follows;possibly inferable from the detailed description; and/or learnable bypractice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of embodiments of the invention and to showhow the same may be carried into effect, reference will now be made,purely by way of example, to the accompanying drawings in which likenumerals designate corresponding elements or sections throughout.

In the accompanying drawings:

FIG. 1A is a high level schematic illustration of various anodeconfigurations, according to some embodiments of the invention.

FIG. 1B is a high level schematic illustration of various anodecomponents in a preparation process, and various anode configurations inthe lithium ion cell, according to some embodiments of the invention.

FIG. 2A is a high-level schematic illustration of a metallizationprocess in prior art lithium ion batteries, according to the prior art.

FIG. 2B is a high level schematic illustration of several processeswhich affect composite anode material particles during batteryoperation, according to some embodiments of the invention.

FIGS. 2C and 2D are high level schematic illustrations of configurationsof anode material particles, according to some embodiments of theinvention.

FIGS. 2E-2G schematically illustrate buffering zones configured toprovide a mobility gradient of anions and/or electron donating groups,according to some embodiments of the invention.

FIGS. 3A-3D are high level schematic illustrations of modified anodeactive material particles, according to some embodiments of theinvention.

FIGS. 4A-4F are high level schematic illustrations of coatings incomposite anode particles, according to some embodiments of theinvention.

FIG. 4G-4J are high level schematic illustrations of in-situpolymerization of conductive polymers, according to some embodiments ofthe invention.

FIGS. 5A and 5B are high level schematic illustrations of lithiumpolymer coatings applied to anode active material particles, accordingto some embodiments of the invention.

FIG. 5C is a high level schematic illustration of a hydrophobic polymercoating applied to pre-lithiated anode active material particles,according to some embodiments of the invention.

FIG. 6 is a high level schematic illustration of composite coatingcomprising interconnected organic and inorganic compounds, according tosome embodiments of the invention.

FIG. 7A is a high level schematic illustration of a core-shell particlewith a composite shell in composite anode material and its advantages,according to some embodiments of the invention—with respect to prior artillustrated schematically in FIG. 7B.

FIG. 7C is a high level schematic illustration of composite anodematerial particles with graphite shells, according to some embodimentsof the invention.

FIG. 7D is a high level schematic illustration of composite anodematerial particles with porous graphite shells, according to someembodiments of the invention.

FIG. 8A is a high level schematic illustration of a core-shell particle,according to some embodiments of the invention.

FIGS. 8B and 8C are high level schematic illustrations of compositeanode material comprising a plurality of core-shell particles, accordingto some embodiments of the invention.

FIG. 8D is a high level schematic illustration of a core-shell particle,according to some embodiments of the invention.

FIG. 8E is a high level schematic illustration of composite anodematerial comprising a plurality of core-shell particles, according tosome embodiments of the invention.

FIG. 8F is a high level schematic illustration of composite anodematerial, according to some embodiments of the invention.

FIG. 9A-9C are high level schematic illustrations of cellconfigurations, according to some embodiments of the invention, comparedwith prior art configurations illustrated in FIG. 9D.

FIGS. 10A-10C and 11A-11C are high level schematic illustrations ofelectrolyte-based buffering zones which may be used in place or inaddition to anode-based buffering zones, according to some embodimentsof the invention.

FIG. 11D is a high level schematic illustration of non-limiting examplesfor bonding molecules, according to some embodiments of the invention.

FIG. 12 is a high level flowchart illustrating a method, according tosome embodiments of the invention.

FIGS. 13A-13C are examples for charging/discharging cycles of anodeswith respect to lithium (half cells), according to some embodiments ofthe invention.

FIGS. 14A-14F are examples for performance of anodes made of modifiedanode active material particles, according to some embodiments of theinvention.

FIGS. 14G-14K are examples for modified anode active material particles,according to some embodiments of the invention.

FIG. 15 presents an example for formation of LTB (lithium tetraborate)in modified anode material particles, according to some embodiments ofthe invention.

FIG. 16A is an example for the surface of an anode produced with in situpolyaniline polymerization disclosed herein, compared to FIG. 16Bshowing an example of a cracked anode surface prepared under similarconditions without polyaniline.

FIGS. 17A and 17B are examples for improved performance of Sn:Si anodesproduced with in situ polyaniline polymerization, according to someembodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the present inventionare described. For purposes of explanation, specific configurations anddetails are set forth in order to provide a thorough understanding ofthe present invention. However, it will also be apparent to one skilledin the art that the present invention may be practiced without thespecific details presented herein. Furthermore, well known features mayhave been omitted or simplified in order not to obscure the presentinvention. With specific reference to the drawings, it is stressed thatthe particulars shown are by way of example and for purposes ofillustrative discussion of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice.

Before at least one embodiment of the invention is explained in detail,it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention is applicable to other embodiments that may bepracticed or carried out in various ways as well as to combinations ofthe disclosed embodiments. Also, it is to be understood that thephraseology and terminology.

Improved anodes and cells are provided, which enable fast charging rateswith enhanced safety due to much reduced probability of metallization oflithium on the anode, preventing dendrite growth and related risks offire or explosion. Anodes and/or electrolytes have buffering zones forpartly reducing and gradually introducing lithium ions into the anodefor lithiation, to prevent lithium ion accumulation at the anodeelectrolyte interface and consequent metallization and dendrite growth.Various anode active materials and combinations, modifications throughnanoparticles and a range of coatings which implement the improvedanodes are provided.

FIG. 1A is a high level schematic illustration of various anodeconfigurations, according to some embodiments of the invention. FIG. 1Aillustrates schematically, in a non-limiting manner, a surface of anode100, which may comprise anode active material particles 110 (e.g.,particles of metalloids such as silicon, germanium and/or tin, and/orpossibly particles of aluminum, lead and/or zinc, and see below for moredetails and possibilities; anode active material particles 110 may alsopossibly comprise composite particles 115 disclosed below in moredetail) at different sizes (e.g., in the order of magnitude of 100 nm,and/or possibly in the order of magnitude of 10 nm or 1μ)—for receivinglithiated lithium during charging and releasing lithium ions duringdischarging. Anodes 100 may further comprise binder(s) and additive(s)102 as well as optionally coatings 130 (e.g., conductive polymers,lithium polymers, etc., see below). Active material particles 110 may bepre-coated by one or more coatings 120 (e.g., by conductive polymers,lithium polymers, etc.), have borate and/or phosphate salt(s) 128 bondto their surface (possibly forming e.g., B₂O₃, P₂O₅ etc., see below),bonding molecules 180 (illustrated schematically) which may interactwith electrolyte 85 (and/or ionic liquid additives thereto, see below)and/or various nanoparticles 112 (e.g., B₄C, WC, VC, TiN see below), maybe attached thereto in anode preparation processes 105 such as ballmilling (see, e.g., U.S. Pat. No. 9,406,927, which is incorporatedherein by reference in its entirety), slurry formation, spreading of theslurry and drying the spread slurry. For example, anode preparationprocesses 105 may comprise mixing additive(s) 102 such as e.g.,binder(s) (e.g., polyvinylidene fluoride, PVDF, styrene butadienerubber, SBR, or any other binder), plasticizer(s) and/or conductivefiller(s) with a solvent such as water or organic solvent(s) (in whichthe anode materials have limited solubility) to make an anode slurrywhich is then dried, consolidated and is positioned in contact with acurrent collector (e.g., a metal, such as aluminum or copper). Detailsfor some of these possible configurations are disclosed below.

It is explicitly noted that in certain embodiments, cathodes may beprepared according to disclosed embodiments, and the use of the termanode is not limiting the scope of the invention. Any mention of theterm anode may be replaced in some embodiments with the terms electrodeand/or cathode, and corresponding cell elements may be provided incertain embodiments. For example, in cells 150 configured to provideboth fast charging and fast discharging, one or both electrodes 100, 87may be prepared according to embodiments of the disclosed invention.

Certain embodiments comprise composite anode material particles 115which may be configured as core shell particles, as disclosed below. Thedifferent configurations are illustrated schematically in differentregions of the anode surface, yet embodiments may comprise anycombinations of these configurations as well as any extent of anodesurface with any of the disclosed configurations. Anode(s) 100 may thenbe integrated in cells 150 which may be part of lithium ion batteries,together with corresponding cathode(s) 87, electrolyte 85 and separator86, as well as other battery components (e.g., current collectors,electrolyte additives—see below, battery pouch, contacts, and so forth).

Anode material particles 110, 110A, 115, anodes 100 and cells 150 may beconfigured according to the disclosed principles to enable high chargingand/or discharging rates (C-rate), ranging from 3-10 C-rate, 10-100C-rate or even above 100 C, e.g., 5 C, 10 C, 15 C, 30 C or more. It isnoted that the term C-rate is a measure of charging and/or dischargingof cell/battery capacity, e.g., with 1 C denoting charging and/ordischarging the cell in an hour, and XC (e.g., 5 C, 10 C, 50 C etc.)denoting charging and/or discharging the cell in 1/X of an hour—withrespect to a given capacity of the cell.

FIG. 1B is a high level schematic illustration of various anodecomponents in a preparation process 105, and various anodeconfigurations in lithium ion cell 150, according to some embodiments ofthe invention. FIG. 1B illustrates schematically, in a non-limitingmanner, a surface of anode 100, which may comprise anode active materialparticles 110 (e.g., shell-core particles 115 with cores 110 beingparticles of metalloids such as silicon, germanium and/or tin, and/or ofaluminum, or cores made of other materials, listed below) at differentsizes (e.g., in the order of magnitude of 100 nm, and/or possible in theorder of magnitude of 10 nm or 1 μm), binder(s) 102 (for bindingparticles 110 and/or 115 in the anode material to each other and to thecurrent collector, not shown) and additive(s) 102 as well as optionallycoating(s) 130A and/or conductive fiber(s) 130 (e.g., conductivepolymers, lithium polymers, carbon fibers etc. and see details below).Active material particles 110 may be pre-coated 120 (in one or morelayers 120, e.g., by conductive polymers, lithium polymers, etc., B₂O₃,P₂O₅, etc., see details below) and/or various nanoparticles (e.g., B₄C,WC etc., see details below) 112, may be attached thereto in preparationprocesses 105 such as ball milling (see, e.g., U.S. Pat. No. 9,406,927,which is incorporated herein by reference in its entirety), slurryformation, spreading of the slurry and drying the spread slurry. Detailsfor some of these possible configurations are disclosed in the patentdocuments which were listed herein. The different configurations areillustrated schematically in different regions of the anode surface, yetembodiments may comprise any combinations of these configurations aswell as any extent of anode surface with any of the disclosedconfigurations.

In the illustrated configurations, conductive fibers 130 are shown toextend throughout anode 100, interconnect cores 110 and interconnectedamong themselves. Electronic conductivity may be enhanced by any of thefollowing: binder and additives 102, coatings 130A, conductive fibers130, nanoparticles 112 and pre-coatings 120, which may be in contactwith an electronic conductive material (e.g., fibers) 130. Lithium ioncell 150 comprises anode 100 (in any of its configurations disclosedherein) comprising anode material with composite anode material such ascore-shell particles 115, electrolyte 85 and at least cathode 87delivering lithium ions during charging through cell separator 86 toanode 100. Lithium ions (Li⁺) are lithiated (to Li^(˜01), indicatingsubstantially non-charged lithium, in lithiation state) when penetratingthe anode material, e.g., into anode active material cores 110 ofcore-shell particles 115. Any of the configurations of composite anodematerial and core-shell particles 115 presented below may be used inanode 100, as particles 115 are illustrated in a generic, non-limitingway. In core-shell particle configurations 115, the shell may be atleast partly be provided by coating(s) 120, and may be configured toprovide a gap 140 for anode active material 110 to expand 101 uponlithiation. In some embodiments, gap 140 may be implemented by anelastic or plastic filling material and/or by the flexibility ofcoating(s) 120 which may extend as anode active material cores 110expands (101) and thereby effectively provide room for expansion 101,indicated in FIG. 1B schematically, in a non-limiting manner as gap 140.Examples for both types of gaps 140 are provided below, and may becombined, e.g., by providing small gap 140 and enabling further placefor expansion by the coating flexibility.

Examples for electrolyte 85 may comprise liquid electrolytes such asethylene carbonate, diethyl carbonate, propylene carbonate,fluoroethylene carbonate (FEC), EMC (ethyl methyl carbonate), DMC(dimethyl carbonate), VC (vinylene carbonate) and combinations thereofand/or solid electrolytes such as polymeric electrolytes such aspolyethylene oxide, fluorine-containing polymers and copolymers (e.g.,polytetrafluoroethylene), and combinations thereof. Electrolyte 85 maycomprise lithium electrolyte salt(s) such as LiPF₆, LiBF₄, lithiumbis(oxalato)borate, LiN(CF₃SO₂)₂, LiN(C₂F₅SO₂)₂, LiAsF₆, LiC(CF₃SO₂)₃,LiClO₄, LiTFSI, LiB(C₂O₄)₂, LiBF₂(C₂O₄), tris(trimethylsilyl)phosphite(TMSP) and combinations thereof. Ionic liquid(s) may be added toelectrolyte 85 as disclosed below.

In certain embodiments, cathode(s) 87 may comprise materials based onlayered, spinel and/or olivine frameworks, and comprise variouscompositions, such as LCO formulations (based on LiCoO₂), NMCformulations (based on lithium nickel-manganese-cobalt), NCAformulations (based on lithium nickel cobalt aluminum oxides), LMOformulations (based on LiMn₂O₄), LMN formulations (based on lithiummanganese-nickel oxides) LFP formulations (based on LiFePO₄), lithiumrich cathodes, and/or combinations thereof. Separator(s) 86 may comprisevarious materials, such as polyethylene (PE), polypropylene (PP) orother appropriate materials. Possible compositions of anode(s) 100 aredisclosed below in detail.

Buffering Zone

FIG. 2A is a high-level schematic illustration of a metallizationprocess in lithium ion batteries according to the prior art. Typicallithium ion batteries use graphite anode material 95 which receiveslithium ions 91 (from an electrolyte 85) in an intercalation processbetween graphite layers. The maximal capacity of the graphite is limitedto approximately one lithium ion for every ca. six carbon atoms and isinfluenced by the solid-electrolyte interface (SEI) formed between anodematerial 95 and electrolyte 85, typically on the intercalation basalplanes (e.g., layers in the graphite material between which the lithiumions intercalate). Such lithium ion batteries typically have lowcharging and discharging rates due to limiting charge transfer rates andlimiting lithium ions diffusion rate into the graphite anode. As shownschematically in illustration 90A in FIG. 2A, under low charging rates,the intercalation rate is higher than the lithium ion accumulation rate,resulting in proper intercalation 96 of lithium ions Li⁺ into graphiteanode material 95 as L^(˜01), denoting approximately neutral lithiumatoms which receive electrons e⁻ from the graphite and are intercalatedin anode material 95. The intercalation rate is limited by the Li⁺supply rate. As the charging rate increases (schematic illustrations90B, 90C, 90D represent increasing charging rate with respect toillustration 90A), the rate of incoming lithium ions increases, andlithium ions accumulate on the surface (of anode material 95 orparticles thereof, at the solid-electrolyte interface) as illustrated in90B, with an accumulation rate that exceeds the intercalation rate ofthe lithium ions. As a result, reduction 97 of the lithium ions iscarried out on the interface in addition to the intercalated lithiumions, as illustrated in 90C, which shows schematically the increasingflow of electrons to the interface without lithium ion intercalation inanode material 95. Finally, as lithium ion accumulation and reduction atthe interface increase (as illustrated in 90D), lithium metallization atthe interface and dendrite growth 99 commence and damage the cell.Additional considerations include volume changes of the graphiteelectrode material, influences of anode additives, characteristics ofthe SEI and details of the charging and discharging cycles.

Embodiments of the present invention provide electrode and cellconfigurations which enable fast charging rates with enhanced safety dueto much reduced probability of metallization of lithium on the anode,preventing dendrite growth and related risks of fire or explosion. Anodematerial particles have buffering zones for partly reducing andgradually introducing lithium ions into the anode for lithiation, toprevent lithium ion accumulation at the anode electrolyte interface andconsequent metallization and dendrite growth. The electrolyte in thecell may be chosen to further reduce the accumulation rate of lithiumions at the interface, and the cell may be designed to have lithiationin the anode material as the rate limiting factor, thereby avoidinglithium ion accumulation at the anode material particles' surface.

FIG. 2B is a high level schematic illustration of several process whichaffect composite anode material particles 115 during battery operation,according to some embodiments of the invention. In many of the disclosedembodiments, the inventors allow for expansion and contraction 101 ofanode material particles 110 during charging and discharging of thebattery (respectively), in order to be able to utilize materials havinghigh capacity for absorbing lithium (such as Si, Ge, Sn, Al, Pb, Zn,their alloys and mixtures, as well as other materials) for energystorage. It is noted that many of the disclosed embodiments are likewiseapplicable to graphite anode material and/or modified graphite anodematerial, with respect to the lithiation process being lithium ionintercalation in the graphite.

Moreover, in many of the disclosed embodiments, the inventors succeed inmaintaining required electronic (e⁻) and ionic (Li⁺) conductivity,schematically denoted 106 and 103, respectively, which enable fastcharging and/or fast discharging the battery, while maintaining themechanical stability of anode material particles 110 and composite anodeparticles 115, e.g., through the use of a range of coatings 120 andadded nanoparticles, as disclosed herein. The notation Li^(δ+) indicatespartially reduced lithium ions, as an intermediate stage between lithiumions Li⁺ and lithium L^(˜01) in lithiated anode material. The partialreduction of Li^(δ+) may result from adjacent negative charges whichpartially reduce the positive charge of Li⁺ Various anode materialconfigurations which enable partial reduction of the lithium ions andresulting advantages are described below in detail. Examples formechanical stability of anode material particles 110 include reductionor lack of cracking of particles 110, e.g., after a certain number(e.g., 50, 100, 500 etc.) of charge/discharge cycles, possibly at fastcharge/discharge rate (e.g., 5 C, 10 C, 50 C, etc.).

FIGS. 2C and 2D are high level schematic illustrations of configurationsof anode material particles 110, according to some embodiments of theinvention. The illustrated configurations may likewise be applicable tocomposite anode material particles 115. The illustrated configurationsmay be implemented in corresponding cells 150 of energy storage devices(e.g., lithium ion batteries) to provide safe cells having high chargingand/or discharging rates, e.g., 5 C, 10 C, 15 C or more.

Anode material particles 110 may be designed to handle the ionaccumulation at the interface between the anode active material andelectrolyte 85 at high charging rates by regulating lithium ionaccumulation as well as by regulating the reduction mechanism of thelithium ion at the interface to reduce the probability of on-surfacemetallization and dendrite growth. Such designs may increase safety byreducing the probability of surface lithium metallization. Withoutintending to be bound by theory, anode material particles 110 mayimplement, by various active material surface modifications, a loweringof the surface energy, and a buffering in the interface for thereduction mechanism of Li⁺ to Li⁰. These mechanisms reduce the lithiumion accumulation at the interface and the reduction of the lithium ionsat the interface which were illustrated schematically in FIG. 2A andwhich lead to surface metallization and dendrite growth.

FIG. 2C schematically illustrates at least one buffering zone 110B(e.g., at least a partial coating 120 or at least part of coating 120)on the surface of anode material particle 110—which separateselectrolyte 85 from an internal anode material particle region 110C,according to some embodiments of the invention. Buffering zone(s) 110Bmay be configured to accumulate lithium atoms with partial charge(denoted by Li^(δ+)), an accumulation which dramatically reduces theprobability of surface lithium metallization. Buffering zone(s) 110B maybe further configured to enable faster and smoother transition of thelithium ions Li⁺ via the partly charge state Li^(δ+) to the lithiatedstate Li^(˜01) in the active material in zone(s) 110C. In disclosedanode configurations, buffering zone(s) 110B may be configured to absorbthe fast diffusion of incoming lithium ions at high charging rates andthus prevent surface accumulation, metallization and dendrite growth oflithium. The dimensions and parameters of buffering zone(s) 110B may beconfigured to buffer an expected amount of lithium ions that is derivedfrom parameters and operation conditions of the battery.

For example, materials in buffering zone(s) 110B may be selected toprovide electrons (e⁻, illustrated schematically by the black dots) atsufficient proximity to the lithium ions to reduce their +1 charge topartial charge δ+ without creating chemical bonds between material ofbuffering zone(s) 110B and lithium ions Li^(δ+)— in order to enabletheir further movement into anode material 110 and being lithiatedtherein and prevent reduction and metallization of them in bufferingzone(s) 110B. Examples for materials in buffering zone(s) 110B are ionicconductors which are medium electronic conductors, such as inorganicborates, phosphates or polyphosphates and organic polymers such aspolypyrrole and polyaniline—the particle size of which and thickness ofbuffering zone(s) 110B may be determined according to specifiedperformance requirements. More examples for material that may constitutebuffering zone(s) 110B are presented below as various coatings 120,which may at least partly be configured to generate buffering zone(s)110B. For example, various conductive polymers, possibly lithiatedpolymers and/or lithiated conductive polymers, may be used as coatings120.

FIG. 2D schematically illustrates at least one buffering zone 110B onthe surface of anode material particle 110 as support for a SEI 122,according to some embodiments of the invention. In certain embodiments,at least one of buffering zone(s) 110B may be configured to provide aflexible skeleton for the formation of SEI 122 (which is typicallybrittle), to improve the stability of SEI 122 during mechanicalexpansion and contraction 101 (SEI deformation illustrated schematicallyby arrows 101A, and see FIG. 2B) of anode material particle 110. Theflexibility of buffering zone(s) 110B, possibly achieved by flexiblematerials such as inorganic structures and/or organic polymers disclosedbelow as coating(s) 120 may be configured to prevent damage to SEI 122undergoing mechanical deformations 101A due to expansion and contraction101 of anode material particle 110 in its operation. For example, atleast some of the anions in buffering zone(s) 110B may be immobile or atleast less mobile than the respective cations in buffering zone(s) 110Bin order to provide a higher electron concentration that provides thepartial charge Li^(δ+) to lithium ions entering buffering zone(s) 110B.

FIGS. 2E-2G schematically illustrate buffering zones 110B configured toprovide a mobility gradient 125 of anions and/or electron donatinggroups 126, according to some embodiments of the invention. In certainembodiments, buffering zone(s) 110B may be configured to provide amobility gradient 125 (indicated schematically by the tapered arrow) ofanions and/or electron donating groups 126 (illustrated schematically asproviding negative charges) which in turn provides a charge gradientthat reduces lithium ions 91 entering buffering zones 110B fromelectrolyte 85 in a gradual manner (indicated schematically by Li^(δ+)expressing the partial screening of the positive charge of Li⁺ inbuffering zones 110B) until they reach lithiation in anode materialparticle 110. Gradient 125 may be configured to enable modification ofthe interface between anode material particle 110 and electrolyte 85(the area where two immiscible phase surfaces are coming in contact witheach other) into an interphase region having a gradual change ofparameters which gradually reduces the activation energy of thereduction reaction of the lithium ions, and further preventsmetallization of lithium and dendrite growth. Coating(s) 120 disclosedbelow may be configured to facilitate and support the interphase regionand thereby regulate lithium ion flow into and out from anode materialparticle 110, especially during fast charging and/or discharging atrates of several C-rate, several tens of C-rate and possible even a fewhundred C-rate.

Buffering zone(s) 110B may be configured to form a barrier which reducesthe speed of lithium ions 91 and locally increases the resistance ofbuffering zone(s) 110B to lithium ions 91 to prevent or attenuatereduction of lithium ions 91 (see r′_(A) in FIG. 9A below). Coating(s)120 disclosed below may be configured to provide the required localresistance.

As illustrated schematically in FIG. 2F, buffering zone 110B may beconfigured to provide negative electric charge at predefined density toreplace a solvation shell 91A of Li⁺ 91 in electrolyte 85 by anequivalent environment 91B within solid buffering zone 110B, which maye.g., comprise coating 120 such as a polymer coating, possibly aconductive polymer coating. For example, coating 120 may compriseelectron donating groups 126 (e.g., atoms such as N or O, having a lonepair of electrons, aromatic groups and/or conjugated systems asdisclosed below etc.) at specified densities, which form environment 91Bwhich partly screens the positive charge of Li⁺ passing throughbuffering zone 110B (denoted schematically as Li^(δ+)). In contrast toprior art SEI's, which impede the entering of lithium ions into theanode material particles by the required removal of solvation shell 91Aupon entering the SEI from the electrolyte, advantageously disclosedbuffering zone(s) 110B and coating(s) 120, by providing equivalentenvironment 91B increase ionic conductivity 103 and enable high chargingrates with reduced or avoided risk for lithium metallization due theprior art SEI impediments. In certain embodiments, buffering zone(s)110B and coating(s) 120 may be configured to provide environment 91Bthat provides enough negative charge to incoming lithium ions to makede-solvation (of the lithium ions from the electrolyte) not the ratelimiting step in the lithiation (charging) process. Without being boundby theory, by relieving the rate limitation of the de-solvation process,buffering zone 110B may prevent prior art metallization of lithium onthe anode particles' surface (see e.g., FIG. 2A, in which de-solvationmay be considered the rate limiting step in the prior art).

FIG. 2G illustrates in a high level schematic fashion a possible spatialarrangement of electron donating groups 126 and non-electron donatinggroups 123 (e.g., groups which do not have free or conjugated electrons)in buffering zone 110B. Only a few groups and a two dimensionalstructure are presented for illustration purposes, clearly realbuffering zone(s) 110B comprise a large number of interconnected groupsin a three dimensional structure. The distance between electron donatinggroups 126 (indicated schematically as D) may be selected (with respectto the statistical properties of coating 120 and other polymerparameters) to increase ionic conductivity 103 and provide environment91B to a sufficient extent that provides required fast charging andsafety parameters. For example, electron donating groups 126 may beseparated by 2-5 non-electron donating groups 123 (e.g., D=2-5non-electron donating groups 123) in the structure of buffering zone110B. The composition and structure of buffering zone 110B may beconfigured to enhance ionic conductivity 103 while maintain electronicconductivity at a level which does not cause metallization of thelithium ions in buffering zone 110B and encourages lithiation of lithiumin anode material 110. For example, buffering zone 110B may beconfigured to have ionic conductivity 103 in the order of magnitude of0.01-10 S/cm or any subrange thereof. Gradient 125 in buffering zone110B may be formed by configuration of coating(s) 120 which providesolid environment 91B which is equivalent to solvation shell 91B inelectrolyte 85, partly mask the positive charge of the lithium ionsmoving therethrough (to Li^(δ+)) and maintain high ionic conductivity103 to deliver the lithium ions to lithiation in anode material 110.

Anode Material

In the following, various material combination embodiments for theactive anode material are presented. It is emphasized that elements fromdifferent embodiments may be combined to form additional embodiments,and that any of the anode active material embodiments may be combinedwith various coating embodiments and anode embodiments disclosed herein.

Silicon Active Material

In some embodiments, anode active material particles 110 may compriseany of Si (silicon), B (boron) and W (tungsten) and/or combinationsthereof as mixtures and/or alloys. In some embodiments, anode activematerial particles 110 may comprise Si at 4-35 weight % of the totalweight of the anode material, e.g., anode active material particles 110may comprise 4-35 weight % Si and/or 4-35% of anode active materialparticles 110 may comprise Si, and/or anode 100 may comprise anycombination thereof. In certain embodiments, B and/or W may be includedin anode active material particles 110 as dopant(s) and/or as attachedparticles or nanoparticles.

In some embodiments, anode active material particles 110 may comprise Bat 2-20 weight % of the total weight of the anode material. In someembodiments, anode active material particles 110 may comprise W at 5-20weight % of the total weight of the anode material. In some embodiments,anode active material particles 110 may comprise C (carbon) at 5-60weight % of the total weight of the anode material, e.g., as any ofspherical carbon particles, CNTs (carbon nanotubes) and grapheneparticles. In certain embodiments, anode active material particles 110may comprise CNTs at 0.05-0.5 weight % of the total weight of the anodematerial. CNTs may be used as part of modified anode active materialparticles 110A, as part of composite anode particles 115 and/or in anode100, as disclosed herein.

In certain embodiments, Si may be used at 2-25 weight % of the totalweight of the anode material and B may be used at 5-18 weight % of thetotal weight of the anode material and/or W may be used at 7-13 weight %of the total weight of the anode material. Conductive materials may beadded to the anode material, e.g., at 0.01-15 weight % of the totalweight of the anode material.

In certain embodiments, Si may be used at 5-47 weight % of the totalweight of the anode material and B may be used at 3-25 weight % of thetotal weight of the anode material and/or W may be used at 6-25 weight %of the total weight of the anode material. Conductive materials may beadded to the anode material, e.g., at 0.01-15 weight % of the totalweight of the anode material.

In certain embodiments, Si may be used at 4-35 weight % of the totalweight of the anode material and B may be used at 2.5-25.6 weight % ofthe total weight of the anode material and/or WC may be used at 7-14weight % of the total weight of the anode material. Possibly, conductivematerials such as carbon may be added to the anode material, e.g., at5-60 weight % of the total weight of the anode material.

The weight % disclosed herein may be with respect to the total materialof any of anode active material particles 110, modified anode activematerial particles 110A (see below, e.g., B may be at least partly usedas B₄C, W may be at least partly used as WC), composite anode particles115 (e.g., the total weight including coating 120), and/or all anodematerial of anode 100. Components of any of the disclosed embodimentsmay be combined in various embodiments.

Binders 102 may be added at 0.1-15 weight % of the total weight of theanode material of anode 100.

Germanium Active Material

In some embodiments, anode active material particles 110 may compriseany of Ge (germanium), B and W and/or combinations thereof as mixturesand/or alloys. In some embodiments, anode active material particles 110may comprise Ge at 5-80 weight % of the total weight of the anodematerial, e.g., anode active material particles 110 may comprise 5-80weight % Ge and/or 5-80% of anode active material particles 110 maycomprise Ge, and/or anode 100 may comprise any combination thereof. Incertain embodiments, B and/or W may be included in anode active materialparticles 110 as dopant(s) and/or as attached particles ornanoparticles.

In some embodiments, anode active material particles 110 may comprise Bat 2-20 weight % of the total weight of the anode material. In someembodiments, anode active material particles 110 may comprise W at 5-20weight % of the total weight of the anode material. In some embodiments,anode active material particles 110 may comprise C (carbon) at 0.5-5, orpossibly up to 10 weight % of the total weight of the anode material,e.g., as any of spherical carbon particles, CNTs (carbon nanotubes) andgraphene particles. In certain embodiments, anode active materialparticles 110 may comprise CNTs at 0.05-0.5 weight % of the total weightof the anode material. CNTs may be used as part of modified anode activematerial particles 110A, as part of composite anode particles 115 and/orin anode 100, as disclosed herein.

In some embodiments, Si may be used to at least partly complement Ge,e.g., at weight ratios of at least 4:1 (Ge:Si). In certain embodiments,other anode active materials disclosed herein may be used to complementGe, e.g., Sn, Al or other materials. For example, Sn may be used toreplace Ge at least partly in the compositions disclosed above. In caseSn, Ge and Si are used for anode material, Si may be used at weightratios of at least 4:1 (Sn+Ge):Si.

In certain embodiments, Ge may be used at 60-75 weight % of the totalweight of the anode material and B may be used at 3-6 weight % of thetotal weight of the anode material and/or W may be used at 7-11 weight %of the total weight of the anode material. Conductive materials may beadded to the anode material, e.g., at 0.01-5 weight % of the totalweight of the anode material.

The weight % disclosed herein may be with respect to the total materialof any of anode active material particles 110, modified anode activematerial particles 110A (see below, e.g., B may be at least partly usedas B₄C, W may be at least partly used as WC), composite anode particles115 (e.g., the total weight including coating 120), and/or all anodematerial of anode 100. Components of any of the disclosed embodimentsmay be combined in various embodiments.

Binders 102 may be added at 0.1-15 weight % of the total weight of theanode material of anode 100.

Tin Active Material

In some embodiments, anode active material particles 110 may compriseany of Sn (tin), Sn and Si, Sn and B, Sn and W and/or combinationsthereof as mixtures and/or alloys. For example, Sn may be used at 5-80weight % of the total weight of the anode material, e.g., anode activematerial particles 110 may comprise 5-80 weight % Sn and/or 5-80% ofanode active material particles 110 may comprise Sn, and/or anode 100may comprise any combination thereof. Si and/or B may be used for therest of the anode material in any of the above combinations. In certainembodiments, B and/or W may be included in anode active materialparticles 110 as dopant(s) and/or as attached particles ornanoparticles.

In some embodiments, B may be used at 2-20 weight % of the total weightof the anode material. In some embodiments, W may be used at 5-20 weight% of the total weight of the anode material. In certain embodiments,carbon may be used at 0.5-5 weight % of the total weight of the anodematerial, e.g., in B₄C and/or WC nanoparticles 112 and/or as conductivematerial 130.

In some embodiments, Si may be used to at least partly complement Sn,e.g., at weight ratios of at least 4:1 (Sn:Si). In certain embodiments,other anode active materials disclosed herein may be used to complementSn, e.g., Ge, Al or other materials. For example, Ge may be used toreplace Sn at least partly in the compositions disclosed above. In caseSn, Ge and Si are used for anode material, Si may be used at weightratios of at least 4:1 (Sn+Ge):Si.

In certain embodiments, Sn may be used at 60-75 weight % of the totalweight of the anode material and B may be used at 3-6 weight % of thetotal weight of the anode material and/or W may be used at 7-11 weight %of the total weight of the anode material. Conductive materials may beadded to the anode material, e.g., at 0.01-5 weight % of the totalweight of the anode material.

In certain embodiments, Sn may be used at 6.5-94 weight % of the totalweight of the anode material and B may be used at 1.5-15 weight % of thetotal weight of the anode material and/or W may be used at 6-25 weight %of the total weight of the anode material.

The weight % disclosed herein may be with respect to the total materialof any of anode active material particles 110, modified anode activematerial particles 110A (see below, e.g., B may be at least partly usedas B₄C, W may be at least partly used as WC) and/or composite anodeparticles 115 (e.g., the total weight including coating 120). Componentsof any of the disclosed embodiments may be combined in variousembodiments.

Non-limiting examples for preparation procedures of tin-containing anodeactive material particles 110 include ball milling of a specified ratioof Sn and Si (as non-limiting examples, any of 1:1, 1:2, 4:1 orintermediate ratios) at a specified milling speed (as non-limitingexamples, any of 200, 300, 400 rpm, or intermediate speeds) for between6 and 12 hours. In certain embodiments, additional milling was performedafter adding 1-20% w/w graphite. The additional milling process wasperformed at a same or different specified milling speed (asnon-limiting examples, any of 200, 300, 400 rpm, or intermediate speeds)for between 6 and 12 hours.

Aluminum Active Material

In some embodiments, anode active material particles 110 may comprisetreated aluminum particles, from which a native surface oxide may beremoved and a lithium-containing surface layer may be applied.

Formation of anode 100 from anode active material particles 110comprising aluminum particles may be carried out by consolidatingtreated aluminum particles 110 with one or more additives, whilepreventing the formation of an oxidation layer on particles 110. Theadditives may comprise, e.g., binders and additives 102 such asparticulate conductive filler(s), plasticizer(s), and/or otherbinder(s); and possibly pre-coating(s) 120, nanoparticles 112 and/orcoating(s) 130.

In certain embodiments, the applied lithium-containing surface layer maybe applied as pre-coating 120, e.g., using lithium polymer(s) such aslithium polyphosphate, lithium poly(acrylic acid), lithium carboxylmethyl cellulose and/or lithium alginate (see below). In certainembodiments, lithium-containing surface pre-coating 120 may compriselithium-aluminum compound(s) having the formula Li_(x)Al_(y), e.g.,Li₉Al₄.

In certain embodiments, B203 may be applied as either pre-coating 120and/or nanoparticles 112 onto the treated aluminum particles, from whichthe native oxide has been removed, in addition or in place of thelithium-containing surface layer.

In certain embodiments, Zn, Cd and/or Pb may be added to any one of thedisclosed embodiments to further increase the lithium capacity of anodeactive material particles 110.

Nanoparticles and Modifications

FIGS. 3A-3D are high level schematic illustrations of modified anodeactive material particles 110A, according to some embodiments of theinvention. Anode active material particles 110 may be modified byattachment or embedment of smaller nanoparticles 112, as illustratedschematically in FIGS. 3A-3D. Embodiments comprise single modified anodeactive material particles 110A (FIGS. 3A, 3C) or aggregates thereof(FIGS. 3B, 3D) which may be used together or separately to prepare anode100. Coatings 120 may be applied on modified anode active materialparticles 110A and/or aggregates thereof to form composite particles 115(FIGS. 3C, 3D respectively), which may be used together or separately toprepare anode 100. The optional embedding of nanoparticles 112 in anodeactive material particles 110 may form an interface layer 114 havingalloy-like characteristics, shown schematically in FIG. 3A.

In some embodiments, anode active material particles 110 may have aparticle size at a range of 30-500 nm, and further comprisenanoparticles 112 (e.g., B₄C, boron carbide, and/or WC, tungstencarbide, nanoparticles) at a range of 10-50 nm on a surface of anodeactive material particles 110 to yield modified anode active materialparticles 110A. Nanoparticles 112 may be configured to reinforce anodeactive material particles 110, e.g., with respect to mechanical forcesof expansion and contraction 101 upon lithiation and de-lithiation oflithium ions (respectively), providing increased mechanical stabilityduring repeated fast-charging/discharging cycles. Alternatively orcomplementarily, nanoparticles 112 may be configured to regulate (e.g.,reduce) the surface energy of modified anode active material particles110A to improve lithium ion conductivity 103, e.g., via providing bettercontact with electrolyte 85; to improve the dispersion of modified anodeactive material particles 110A throughout the anode slurry and thespreading thereof throughout anode 100; and/or to enhance theconsolidation of modified anode active material particles 110A withconductive filler 102 on the current collector.

In certain embodiments, nanoparticles 112 may comprise, additionally orin place of B₄C and/or WC, VC (vanadium carbide), TiN (titanium nitride)and/or equivalent compounds. Nanoparticles 112 may have various effectssuch as partial reduction of lithium ions which may structurallystabilize modified anode active material particles 110A duringlithiation and de-lithiation, improve the electrochemical behavior ofmodified anode active material particles 110A with respect to partialreduction of Li⁺ to Li^(δ+) and prevention of metallization.

In certain embodiments, anode active material particles 110 may compriseany of Sn, Pb, Ge, Si, their alloys and mixtures thereof, having aparticle size in a range of 30-500 nm and B₄C nanoparticles 112 having aparticle size range of 10-50 nm, embedded (114) on the surface of anodeactive material particles 110. The particle size of anode activematerial particles 110 may be in any of the ranges 30-50 nm, 50-100 nm,30-100 nm, 50-200 nm, 100-500 nm or in sub-ranges thereof. Anode activematerial particles 110 may comprise an oxide layer or parts thereof.Alternatively or complementarily, the oxide layer, parts thereof, and/orthe thickness of the oxide layer may be modified during preparation,e.g., by oxidation, heat, reduction and/or combinations thereof, asdescribed herein in various embodiments. Full or partial de-oxidationmay be applied in any of the embodiments of anode active materialparticles 110, e.g., in which Si, Ge, Sn, Al, Pb or other elements areused as the anode active material.

In certain embodiments, the particle size of nanoparticles 112 (e.g.,the B₄C nanoparticles) may be at least one order of magnitude smallerthan the particle size of anode active material (e.g., metalloid)particles 110. In certain embodiments, the amount of nanoparticles 112(e.g., B₄C nanoparticles) may be in the range of 5 to 25 weight percentof anode active material particles 110. Interface layer 114 may comprisea transition metal oxide layer on the surface of active materialparticles 110, which has e.g., a thickness of 1-10 nm.

In certain embodiments, anode active material particles 110 may have anaverage diameter of e.g., 100 nm, 200 nm, 250 nm, 300 nm, 400 nm or 500nm and some, most or all of anode active material particles 110 maycomprise nanoparticles 112, attached thereto and/or embedded therein(depending e.g., on the energy involved in preparation processes 105).Nanoparticles 112 may at least partly cover and/or be embedded in anodeactive material particles 110, with respect to at least a part of thesurface area of anode active material particles 110. For example, ballmilling may yield a powder of anode active material particles 110 withnanoparticles 112 (illustrated schematically in FIG. 3A) and/or ofaggregated anode active material particles 110 (illustratedschematically in FIG. 3B)—to form modified anode active materialparticles 110A.

In certain embodiments, at least some of B₄C nanoparticles 112 mayinteract with metal oxides on the surface of anode active materialparticles 110 to form Li₂B₄O₇ (lithium tetra-borate salt) and/or relatedmaterials as interface layer 114 (see e.g., FIG. 3A) and/or as at leastpart of nanoparticles 112, to further reduce the surface potential ofmodified anode active material particles 110A and possibly leave thesurface thereof partly charged (implementing e.g., buffering zone 110Bin FIGS. 2C, 2E). Partly charged modified anode active materialparticles 110A may then partly reduce lithium ions during charging(Li⁺→Li^(δ+)) and enhance the battery safety by preventing lithiummetallization on the surface of modified anode active material particles110A, as explained herein.

In certain embodiments, any of coatings 120 disclosed herein may beapplied onto modified anode active material particles 110A and/or theiraggregates to form composite particles 115, for example coatings 120 maycomprise amorphous carbon, graphene and/or graphite, covering at leastpartly (or fully) modified anode active material particles 110A. Forexample, coatings 120 may comprise a layer. In certain embodiments,coatings 120 may comprise lithium polymer(s) chemically bonded to thesurface of modified anode active material particles 110A.

Without being bound by theory, the inventors have found out thatnanoparticles 112 and processes 105 for their attachment to anode activematerial particles 110 may be optimized to achieve any of the followingeffects, improving the operation of anodes 100 in lithium ion batteriesand especially in fast charging lithium ion batteries. Nanoparticles 112and processes 105 may be selected and/or configured to increase themechanical stability of anode active material particles 110 by providingan external and/or internal backbone to modified anode materialparticles 110A, especially during expansion and contraction 101 thereofupon lithiation and de-lithiation, respectively. The SEI that may beformed on the surfaces of particles 110 may be more stable and lessbrittle due to the presence of nanoparticles 112. Nanoparticles 112 maybe selected from hard materials (such as B₄C, WC, VC, TiN) and maymoderate expansion and contraction 101, prevent cracking, reduce theamount of agglomeration during multiple charging and discharging cyclesand/or prevent oxidation as described below.

Nanoparticles 112 and processes 105 may be selected and/or configured toprovide any of the following effects. During expansion and contraction101, nanoparticles 112 may be pushed further into modified anodematerial particles 110A, to provide internal mechanical stabilization.Positioned mainly on the surface of modified anode material particles110A, nanoparticles 112 may be selected to lower the surface potentialof modified anode material particles 110A and reduce the rate modifiedanode material particles 110A merge and agglomerate. Reduction ofsurface potential may also provide better contact with electrolyte 85,improving ionic conductivity of the lithium ions into and out ofmodified anode material particles 110A. Moreover, reducing agglomerationalso increases the surface area of modified anode material particles110A which is available to lithium ions movements into and out ofmodified anode material particles 110A, and thereby increases the ionicconductivity and speed of charging and discharging.

In certain embodiments, nanoparticles 112 attached onto anode activematerial particles 110 may form at least a partial shell structure whichallows expansion and contraction 101 of modified anode materialparticles 110A, as illustrated below concerning composite anode materialparticles 115.

In certain embodiments, nanoparticles 112 and processes 105 may beselected and/or configured to reduce or remove oxides of the anodeactive material which may be present and/or may evolve in anode 100, byforming instead compounds such as Li₂B₄O₇ (lithium tetra-borate salt,e.g., via a reaction such as 4Li+7MeO+2B₄C→2Li₂B₄O₇+C+7Me, reaction notbalanced with respect to C and O, with Me denoting active material suchas Si, Ge, Sn etc. and carbon originating from additives) or equivalentcompounds selected from e.g., WC, VC, TiN, which have higher affinity tooxygen than the anode active material. Preventing oxidation not onlyincreases the available active material surface area for lithiation butalso helps prevent metallization of lithium on the surface of modifiedactive material particles 110A.

In certain embodiments, coatings 120, such as illustrated e.g., in FIGS.3C, 3D, may further enhance electronic and/or ionic conductivity. Forexample, thin films (e.g., 1-50 nm, or 2-10 nm thick) of carbon (e.g.,amorphous carbon, graphite, graphene, etc.) and/or transition metaloxide(s) (e.g., Al₂O₃, B₂O₃, TiO₂, ZrO₂, MnO etc.) may be added tomodified anode material particles 110A and/or their aggregates to formcomposite active material particles 115, as disclosed in additionalexamples below. Any of coatings 120 disclosed below may be applied ontomodified anode material particles 110A comprising nanoparticles 112.

In certain embodiments, coating(s) 120 may be configured to provide gaps140 for expansion and contraction 101 and/or may be flexible to allowfor expansion and contraction 101, as disclosed below (see e.g., FIGS.8A, 8D).

In certain embodiments, coating(s) 120 may be configured to support andstabilize a SEI (as illustrated schematically, e.g. in FIG. 2D),preventing cracks therein and preventing particles from merging into oneanother, thereby maintaining a large active material surface area.

In certain embodiments, nanoparticles 112 and processes 105 may beselected and/or configured to reduce potential decomposition ofelectrolyte solvent by carbon coating(s) 120, through the closeproximity of nanoparticles 112 and coating 120, which decreases itssurface potential and the carbon's reactivity towards the electrolytesolvent.

Coating(s) 120 of transition metal oxide(s) (e.g., Al₂O₃, B₂O₃, TiO₂,ZrO₂, MnO etc.) may further enhance mechanical stability of modifiedactive material particles 110A, and may be combined with othercoating(s) 120 disclosed below to form composite active materialparticles 115. Transition metal oxide coating(s) 120 may be furtherconfigured to provide buffering zone 110B and prevent lithiummetallization as described above, and possibly increase ionicconductivity of composite active material particles 115.

In certain embodiments, nanoparticles 112 and processes 105 may beselected and/or configured to prevent prior art disadvantages of usingtransition metal oxide coating(s) 120, by stabilizing the SEI andpreventing crack formation. Combining nanoparticles 112 and transitionmetal oxide coating(s) 120 may provide an improved mechanical skeletonfor composite active material particles 115 (e.g., a stable shellstructure, as shown below) which provides sufficient mechanical supportand maintains anode performance at high C rates, e.g., 2 C, 5 C, 10 C orpossibly tens or even a few hundred C.

In certain embodiments, nanoparticles 112 may complement and/or replacedoping of anode active material particles 110 with B and/or W and mayachieve similar or complementary effects with respect to reduction ofthe surface potential and reactivity toward the electrolyte.

FIGS. 14A-14F presented below are examples for performance of anodes 100made of modified anode active material particles 110A, according to someembodiments of the invention.

Coatings

In the following, various material combination embodiments for coatingsare presented. For example, various conductive polymers, possiblylithiated polymers and/or lithiated conductive polymers, may be used ascoatings 120. It is emphasized that elements from different embodimentsmay be combined to form additional embodiments, and that any of thecoatings embodiments may be combined with various anode active materialembodiments and anode embodiments disclosed herein. Some of thedisclosed coatings may be applied as coatings 120 and/or as coatings130, depending on the exact details of the applied processes.

FIGS. 4A-4F are high level schematic illustrations of coatings 120 incomposite anode particles 115, according to some embodiments of theinvention. Coatings 120 are illustrated in three different forms in thefigures, namely as spherical coating 120 (e.g., in FIGS. 4A, 4C, 4E), aswriggly lines indicating coating 120 (e.g., in FIGS. 4B, 4C, 4E, 4F),and as a thicker line indicating a surface layer coating 120 (e.g., inFIG. 4D, as well as 3C, 3D). These illustrations are used to illustratecoating(s) schematically, and in certain embodiments may representequivalent and/or complementary coatings 120. Any of coatings 120disclosed below may be understood and partial or full coating ofdifferent thickness. Coating 120 may comprise multiple coating layers120A, 120B, which are not limited to the illustrated two layeredcoatings. Any of disclosed coatings 120 may be applied to one or morecoating layers, each of which may be partial or full coating withrespect to the surface of anode active material particles 110.

It is emphasized that any of disclosed coatings 120 may be applied toeither or both anode active material particles 110 and modified anodeactive material particles 110A (the latter illustrated explicitly inFIG. 4F). Moreover, in case of very partial coatings 120 (sparsecoatings 120) coated particles may be understood as modified anodeactive material particles 110A rather than as composite anode particles115, as indicated e.g., in FIGS. 4B, 4F.

In some embodiments, coating(s) 120 may build one or more shell(s) 120with respect to cores of anode active material particles 110 and/ormodified anode active material particles 110A. In this respect,composite anode particles 115 may form core-shell particles 115, withcoating 120 providing at least part of the shell structure and the anodematerial providing at least part of the core structure.

Conductive Coatings

FIG. 4G-4J are high level schematic illustrations of in-situpolymerization of conductive polymers, according to some embodiments ofthe invention.

Conductive coatings 120, as well as conductive polymer coatings and/ormatrix 130 may be used to improve anode conductivity, as well as toimprove structural and mechanical properties of anode 100. Disclosedcoatings 120, 130, such as coatings with conductive polymers, may beapplied to any of the disclosed anode active materials, such as any ofSi, Sn and Ge, their mixtures (in various ratios), combinations andalloys, as well as other anode active materials disclosed herein.Non-limiting examples are Si:Sn anode active materials mixed at ratiosof at 1:1, 2:1, or other ratios, as well as mixtures thereof with Ge.

FIG. 4G is a high level schematic illustration of in-situ polymerizationof conductive polymers, according to some embodiments of the invention.A slurry 107 may comprise monomers 127 (or possibly at least partlyoligomers), active material particles 110 and possibly additives 102 andbe used (105) to form anode 100. The conductive polymers resulting fromthe polymerization of monomers 127 may form particle coatings 120 and/ormatrix 130 in which particles 110 are embedded. In certain embodiments,linker(s) 119 may be added to bind at least some of anode materialparticles 110 to the conductive polymer.

FIG. 4I is a high level schematic illustration of additional benefits ofusing monomers 127 (or possibly oligomers) in slurry 107 according tosome embodiments of the invention, with respect to an approach,illustrated in FIG. 4H, in which polymers 98A are used in slurry 98. Inthe latter approach (FIG. 4H) dispersion of anode material particles 110and additives 102 is non-uniform and requires using a surfactant toachieve more even dispersion. Surprisingly, the inventors have found outthat using monomers 127 (or possibly oligomers) in slurry 107contributes to dispersion of anode material particles 110 and/oradditives 102 (illustrated schematically in FIG. 4I) and results in amore uniform distribution thereof in polymerized matrix 130. Thedispersion of anode material particles 110 was observed visually astransparent slurry when using monomers 127 with respect to using polymer98A in slurry 98 which resulted in turbid slurry due to agglomeration ofanode material particles 110.

FIG. 4J is a high level schematic illustration of binding anode materialparticles 110 by linker molecules 119, according to some embodiments ofthe invention. Linker molecules 119 provide at least partial chemicalattachment of anode material particles 110 to matrix 130, which may bestronger and more stable than physical attachment achieved in themilling process. The resulting stabilization may contribute to higherlevel of uniformity of anode 100 and its better mechanical handling ofexpansion and contraction stresses (101) during lithiation andde-lithiation.

In certain embodiments, polymer coatings may be polymerized in situ, inanode 100, in the presence of anode active material—to create coating120 and/or matrix 130 of the conductive polymer surrounding activematerial particles 110. Polymerization may be configured to yieldcoatings 120 and/or coatings 130 (coatings 130 may function as matrix130 and/or as anode coatings, as explained below), and may be configuredto provide multiple contributions to the structure of anode 100, such asholding together active material particles 110, 110A and/or 115,complementing or possibly replacing binder(s) 102—e.g., to improve cyclelife; and/or increasing anode conductivity as conductive additive 102and/or 130, as polyaniline in the emeraldine form has high electricalconductivity—e.g., to improve the rate capability at high currents. Incertain embodiments, other conductive polymers may be used in additionor in place of polyaniline.

Certain embodiments comprise a method of forming anode material forLi-ion batteries comprising adding an acidic solution to anode activematerial particles 110; adding aniline; stirring the acidic solution(e.g., for at least one hour); and adding a basic solution (e.g., NaOH,KOH, LiOH or any other base) to the stirred acidic solution until aspecified basic pH (in embodiments, a pH of about 9) is achieved—to formpolyaniline as coating 120 and/or as matrix 130. The method may furthercomprise separating polyaniline matrix 130 (including anode activematerial particles 110) from the solution and drying it to form anode100.

In certain embodiments, aniline derivatives may be used, for example,some or all of the added aniline monomers may be substituted by one ormore sulfonic functional groups. The sulfonic functional groups may beselected to improve the adhesion between the polyaniline and the activematerial by chemically binding the active material. In some embodimentsthe aniline may be replaced, partly or completely, by monomers of otherconducting polymers.

In some embodiments, the acidic solution may be a strong acid such asHCl, HNO₃, H₃PO₄ and other phosphate or polyphosphate acids and/orequivalent acids. Phosphate and polyphosphate acids, being slightlybulky, may increase capacity and electric conductivity. In certainembodiments, phosphate and/or polyphosphate acids may be used as polymerdopants.

In certain embodiments, NH₄S₂O₈ (or possibly equivalent salts orperoxides) may be added to the acidic solution with the anilinemonomers, to promote polymerization.

In certain embodiments, polymerization may be performed, alternativelyor complementarily, by oxidative polymerization, polycondensation,electrochemical polymerization or any other polymerization.

In certain embodiments, linkers 119 may be used to bind the polyanilineto anode active material particles 110, as illustrated schematically inFIG. 4G. FIG. 4G schematically illustrates a linker 119 binding apolymer as coating 120 and/or 130 to anode active material particle(s)110, according to some embodiments of the invention. In someembodiments, linker molecules 119 may be added after the polymerizationis completed, e.g., after conductive polymer (e.g., polyaniline) matrix130 is separated and dried. Linkers 119 may have carboxylic groups whichchemically bind to the oxides of active material particles 110 and toconductive polymer matrix 130, e.g., to the lone electron pair on anitrogen of the aniline monomers in polyaniline. Linker molecules 119may also have sulfonate groups, or other groups, which may also bind tothe active material oxides. Due to the chemical binding, linkers 119 mayincrease conductivity and stability and provide flexibility to theelectrode matrix, e.g., stability when the expansion of the activematerial occurs during cycling. Linker molecules 119 may comprise5-sulfoisophthalic acid or its derivatives, succinic acid or otherdicarboxylic acids. In some embodiments, dried slurry 107 may be mixedwith linker molecules 119 in the presence of a solvent (e.g., water).

Anodes 100 may be formed of various active materials, e.g., Si, Si:Sn atvarious ratios, e.g., 1:1 and 2:1 ratios, possibly mixed with Ge, andfor various ratios of aniline to active material. Certain embodimentscomprise addition of MoS₂, e.g., as additives 102, to increase thecapacity of anode 100 (possibly due to an increase in ionicconductivity). Certain embodiments comprise addition of carbon nanotubes(CNTs), e.g., as additives 102, to improve the electronic and ionicconductivity. Certain embodiments comprise pre-lithiation by replacingNaOH in the procedure with LiOH in order to add Li ions to anode 100.Certain embodiments comprise adding 5-sulfoisophthalic acid and/oradding sulfonic functional group(s) on the aniline to improve theadhesion between the polyaniline and the active material.

Advantageously, methods and anodes are provided in which matrix 130 of aconductive polymer surrounding the active material iscreated—independently as coating 130 and/or in relation to anodematerial coatings 120. The polymerization process may be performedin-situ, in the presence of the active material. Advantageously, matrix130 may be configured to both hold together active material particles110, 110A and/or 115, which may cooperate with and/or replace binder102, and also act as a conductive additive to the electrode, such asanode 100. The binding quality of the polymer helps hold the electrodetogether while cycling thus improving cycle life. The conductivityimproves the rate capability even at high currents. Polyaniline may bein emeraldine form which contributes to the high electricalconductivity.

Advantageously, provided matrices 130 were found to overcome crackingand adhesion problems in prior art examples, with polyaniline reducingthe amount of cracking drastically—as illustrated in FIG. 16A withrespect to prior art FIG. 16B (see images below).

Lithium Polymers and Prelithiation

In certain embodiments, coating 120 may comprise lithium-containingpolymer(s) bonded to the surface of anode active material particles 110(and/or modified anode active material particles 110A). In certainembodiments, anode active material particles 110 may be pre-lithiated byintroducing lithium ions into anode active material particles 110 andcoating them by hydrophobic polymer layer 120 which conducts electronsand ions, and enables applying anode preparation processes 105 in spiteof the high reactivity of the lithium ions. Anode 100 may then beprepared from a slurry comprising the coated anode material particles110, coating 120 preventing the lithium ions from chemically reactingwith water molecules in the slurry. Any of the disclosed anode activematerial particles 110 may be coated as disclosed below, e.g., Si, SnSi,Ge and Ge with B₄C anode materials disclosed herein.

FIGS. 5A and 5B are high level schematic illustrations of lithiumpolymer coatings 120 applied to anode active material particles 110,according to some embodiments of the invention. FIG. 5C is a high levelschematic illustration of hydrophobic polymer coating 120 applied topre-lithiated anode active material particles 110, according to someembodiments of the invention.

Lithium Polymers

In certain embodiments, the lithium-containing polymer may comprisenegatively charged group(s) bonded to the surface of anode activematerial particles 110 and lithium groups on the polymer having apartial positive charge. For example, as illustrated schematically inFIGS. 5A and 5B with anode active material as metalloid (such as Si, Ge,Sn, combinations and/or alloys thereof, and in certain embodiments alsoPb, Al, Zn, combinations and/or alloys thereof), an interfacial reactionmay chemically bind lithium polymer 120 to the surface of anode activematerial particles 110. The interfacial reaction may be carried oute.g., in dry conditions inside a ball miller using lithium polymer withmany lithium salt sites, alternatively or complementarily, usingphysical vapor deposition or equivalent processes.

For example, the lithium-containing polymer may comprise any of lithiumpolyphosphate (Li_((n))PP or LiPP), lithium poly-acrylic acid(Li_((n))PAA or LiPAA), lithium carboxyl methyl cellulose (Li_((n))CMCor LiCMC), lithium alginate (Li_((n))Alg or LiAlg) and combinationsthereof, with (n) denoting multiple attached Li.

In some embodiments, a positively charged lithium (Li⁺) of the lithiumpolymer salt may be used to bind the polymer to the active material,reacting on the alloy material surface to bind the negatively chargedanion of the polymer, leaving a partly charged entity (denoted Li^(δ+)to express partial screening of the positive charge of Li⁺ by anionsand/or electron donating groups; and see also FIG. 2C as embodiment ofbuffering zone 110B; and FIGS. 2E-2G disclosing gradient 125 withpolymer anions and/or electron donating groups which provide negativecharge 126) chemically bound to the surface, coating anode activematerial particles 110. As illustrated schematically in FIG. 2C, anionic nature of the SEI/polymer interface may decrease the surfaceenergy by leaving the interfacial lithium ions with positive or partlypositive charge to form gradient 125 (e.g., an intermediate stagebetween ionic and covalent bond and/or an intermediate stabilizedspecies in between fully charged (Li⁺) and neutral (Li⁰) states oflithium). Gradient 125 may reduce or prevent lithium metallization anddendrites formation, especially during fast charge where the anodesurface is likely to face under-potential (see e.g., FIGS. 13A-C and therelated explanations).

In certain embodiments, lithium polymer coating 120 may have a directchemical and/or partial chemical bonding to the active material. Incertain embodiments, Li-polymer coating 120 bonded to the surface ofanode active material particles 110 may be configured to serve as abackbone for the SEI growth which provides flexibility and stability tothe fragile SEI 122, as illustrated schematically in FIG. 2D. Moreover,coating 120 (and its preparation process 105) may be configured to leavesome of the lithium ions sites on the polymer without binding to thesurface, to enable fast ionic transport between electrolyte 85 and anodeactive material particles 110. Polymeric coating 120 may further be ableto support an increased material load and thickening of anode 100 (e.g.,due to SEI formation of SEI 122), possibly even up to 3 mg/cm² or above,without losing performance.

In some embodiments, a physical evidence for the effectiveness oflithium polymeric coating 120 for surface protection of anode activematerial particles 110 was seen while monitoring the viscosity stabilityof the active material in the electrode slurry (e.g., water-based slurryfor example) during anode preparation process 105. For example, withoutpolymeric coating the slurry's viscosity was stable for approximately 1hour. However, after coating anode active material particles 110 withLi-polymer coating 120, the slurry did not change its viscosity even aweek after the preparation.

In certain embodiments, illustrated schematically e.g., in FIGS. 4C and4D, lithium-containing polymer(s) coating 120A may be further coatedwith a layer 120B of carbon and/or transition metal oxide, e.g., a thinlayer thereof. Alternatively or complementarily, in certain embodiments,layer(s) 120A of carbon and/or transition metal oxide may be furthercoated by lithium-containing polymer(s) coating 120A. In someembodiments, coating 120 may comprise lithium-containing polymers withadditional coating elements, e.g., any of carbon, transition metal oxideand/or borate or phosphate salts, as disclosed below.

Direct Pre-Lithiation

Pre-lithiated anodes 100 and methods of pre-lithiating anodes 100 areprovided, in which anode active material particles 110 are coated byhydrophobic polymer layer 120 which is electron and ion conductive.Hydrophobic polymer layer 120 is configured to prevent the lithium ionsfrom chemically reacting with water molecules in the slurry and/orhumidity, to provide pre-lithiated anodes 100 which improve theoperation of lithium ion cells 150 by preventing accumulation of lithiumions (from cathode 87) in anode 100. Anode active material particles 110may further comprise alloyed boron carbide nanoparticles 112 or lithiumtetraborate, and may possibly be coated by a graphene-like layer 120B toreduce reactivity toward electrolyte 85. Coating 120 of anode materialparticles 110 by hydrophobic polymer coating 120 may be carried outmechanically, e.g., by dry ball milling.

Certain embodiments comprise coating lithium-doped anode active materialparticles 110 comprising e.g., any of Si, Ge, Sn, Al, Pb, Zn, Cd, andmixtures and alloys thereof, with coating 120 comprising hydrophobicpolymer layer(s) bonded thereto.

In certain embodiments, hydrophobic polymer layer(s) coating 120A may befurther coated with a layer 120B of carbon and/or transition metaloxide, e.g., a thin layer thereof (e.g., a 1-10 nm carbon layer). Thehydrophobic polymer(s) may be bonded to the lithium ions in anode activematerial particles 110 and at least partly protect them from contactingwater in the anode slurry and/or water vapor in the air. In certainembodiments the hydrophobic polymer(s) contains conjugated aromaticgroups and is electron-conducting and/or ion-conducting.

FIG. 5C is a high level schematic illustration of hydrophobic polymercoating 120C applied to pre-lithiated anode active material particles110, according to some embodiments of the invention.

Pre-lithiated anode material particles 110 which contain lithium ionsLi⁺ e.g., as Si_(x)Li_(y), Al_(z)Li_(n), etc., may be coated byhydrophobic polymer layer 120C configured to prevent the lithium ionsfrom chemically reacting with water molecules surrounding anode materialparticles 110 and/or with humidity, and to conduct electrons (e⁻) andions, e.g., Li⁺ It is noted that coated anode material particles 115 (or110A) may also be used in dry environment, low humidity environmentand/or in non-aqueous slurry. It is also noted that the degree ofpre-lithiation of anode material particles 110 may vary, e.g., be fullor partial pre-lithiation.

Attaching hydrophobic polymer 120C onto anode material particles 110 maybe carried out by providing an appropriate amount of energy which formsmultiple bonds therebetween, e.g., multiple relatively weak bonds whichtogether maintain polymer 120 attached to anode material particles 110.For example the bonds may be oxide bonds between polymer molecules andthe anode material, possibly involving lithium ions (Li⁺) of thepre-lithiated anode material and/or lithium ions (Li⁺) attached to thepolymer. Hydrophobic polymer layer 120C may comprise lithium ions whichare bonded to hydrophobic polymer 120. For example, for a case in whichthe monomers are bonded to lithium ions, the anode material may favorthe lithium ions in the polymer salt, which lithiate the surface leavingthe lithium ions partly charged on the anode material particles'surface, and hence chemically bond the anionic part of the polymerdirectly to the metalloid surface of anode material particles 110.

Attaching of polymer 120 onto anode material 110 may be carried out bysolid phase interfacial reaction due to favorable Li⁺ to metalloid/metaloxide interaction. For example, dry ball milling may be used for theattaching, configured to provide sufficient energy for creating thebonds, while being carried out at energy that maintains anode materialparticles 110 and the polymer's monomer intact (e.g., not reduced insize and maintaining the molecular structure, respectively). Theinventors note that solid phase reactions may in certain embodiments beimplemented for the attaching of polymers to provide coatings 120.

In certain embodiments, the attaching may be carried out thermally,e.g., by providing the required energy thermally.

Advantageously, as illustrated in FIG. 5C by coated anode materialparticles 115, the attaching provides polymer 120 as a stable backbonefor the SEI (Solid-Electrolyte Interface) formation in the operatingcell with disclosed anodes, enabling fast ionic transport, flexibilityand SEI stability during many cycles in the operating cell (asillustrated schematically in FIGS. 2C-2G). The inventors expect thatcoated anode material particles 115 have a TEM (transmission electronmicroscopy) image indicating a uniform coating of anode materialparticles 110 by polymer 120.

Anode active material particles 110 may comprise metalloids such assilicon, germanium, tin, lead, zinc and cadmium. In certain embodiments,anode material particles 110 may comprise any of silicon, germanium, tinas well as oxides and/or alloys thereof. In certain embodiments, anodeactive material particles 110 may comprise any of various metal oxides.

Hydrophobic polymer layer 120C may be prepared from hydrophobic polymerscomprising e.g., conjugated aromatic groups, such as polypyrroles,polyanilines and other hydrophobic, electron and ion conducting polymersand/or polymers comprising electron and ion conducting substituents. Itis emphasized that hydrophobic polymer layer 120C may be free oflithium, particularly when anode material particles 110 are fullypre-lithiated.

Advantageously, coating anode material particles 110 by hydrophobicpolymer layer 120 enables pre-lithiating anode material in spite of thehigh reactivity of lithium ions to water in slurries used to manufacturethe anode. The hydrophobic protection enables production of anodes underless strict dryness conditions than those required when handling lithiumdirectly, and thereby simplifies the production process of pre-lithiatedanodes while providing the benefits as cell anodes which include higherperformance and longer operation efficiency.

In certain embodiments, pre-lithiation may be applied to any of anodematerial particles 110 disclosed herein. For example, pre-lithiation maybe applied to anode active material particles 110 in the range of 30-50nm, 30-100 nm, 50-200 nm, 100-500 nm and/or 500-1000 nm (pre-lithiationmay enable and/or require using particles in the larger range) and be atleast partially covered (e.g., coated, doped) with B₄C (boron carbide)nanoparticles 112 of smaller scale (e.g., one order of magnitude smallerthan the metalloid particle), for example, 10-50 nm, as described above.B₄C nanoparticles 112 may be at least partially embedded on the surfaceof anode material particles 110, as illustrated schematically in FIG.5B. Polymer coating 120 may be applied on anode material particles 110and cover B₄C nanoparticles 112 as well. B₄C nanoparticles 112 may bealloyed to anode material particles 110 (illustrated schematically byregion 114 where B₄C nanoparticle 112 contacts anode material particle110), thereby further lowering the surface energy of particles 115 andpreventing metallization and/or enhancing polymer binding by keeping thelithium ions on the surface partly positive.

Certain embodiments comprise multi-layered coated anode materialparticles 115 having an additional graphene-like coating 120B (see e.g.,FIG. 4E, made of e.g., amorphous carbon, graphite, graphene etc.) may beapplied on top of polymer 120, e.g., by mechanical grinding of graphiteto form a multi-layered graphene-like coating on top of polymer 120.Graphene-like coating 120B may be applied on top of polymer layer 120(optionally when applied to anode material particles 110A with embeddedB₄C nanoparticles 112) to further reduce the surface potential ofparticles 115 and make them less reactive to electrolyte 85, therebyreducing the probability for catalytic reaction with the electrolyte andincreasing the lifetime of cell 150 and energy storage devices (such asbatteries) produced therefrom.

Borates and/or Phosphates

In certain embodiments, coating 120 may comprise any of boron oxide(s),phosphorus oxide(s), borate(s), phosphate(s) and combinations thereof.For example, coating 120 may have a thickness between 2-200 nm, and beapplied onto anode active material particles 110 (and/or modified anodeactive material particles 110A) having a diameter in the range between20-500 nm (thicker coatings 120 generally apply to larger particles110). For example, coating 120 may comprise borate salt crystals and/orphosphate salt(s) applied onto anode active material particles 110 madeof any of Si, Sn, Ge, Pb, Al, mixtures thereof, and alloys thereof.

In certain embodiments, boron and/or phosphorous containing coating 120Amay comprise borate and/or phosphate salt(s) 128 disclosed below. Incertain embodiments, boron and/or phosphorous containing coating 120Amay be further coated with a layer 120B of carbon and/or transitionmetal oxide, e.g., a thin layer thereof. In certain embodiments, any ofthe disclosed borate/phosphate coatings may be combined with any of thedisclosed polymer coatings, as illustrated schematically in FIG. 6below.

In certain embodiments, borate and/or phosphate salt(s) 128 may compriseborate salts such as lithium bis(oxalato)borate (LiBOB, LiB(C₂O₄)₂),lithium bis(malonato)borate (LiBMB), lithiumbis(trifluoromethanesulfonylimide) (LiTFSI). lithiumdifluoro(oxalato)borate (LiFOB, LiBF₂(C₂O₄)), lithium tetraborate(LiB₄O₇) or any other compound which may lead to formation of borateoxides (B₂O₃) (or related salts) on anode active material particles 110,including in certain embodiments B₄C nanoparticles 102.

In certain embodiments, borate and/or phosphate salt(s) 102A maycomprise phosphate salts such as lithium phosphate (LiPO₄), lithiumpyrophosphate (LiP₂O₇), lithium tripolyphosphate (LiP₃O₁₀) or any othercompound which may lead to formation of phosphate oxides (P₂O₅) (orrelated salts) on anode active material particles 110.

The diameter of anode active material particles 110 may be e.g., between20-500 nm, for example having an average particle size of 50 nm, 100 nm,200 nm, 250 nm, 300 nm, 400 nm or more. The thickness of layer 120 ofborate and/or phosphate salt(s) 102A and/or of borate oxides (B₂O₃,and/or related salts) and/or phosphate oxides (P₂O₅, and/or relatedsalts) formed therefrom of the surface of anode active materialparticles 110 may be between 2-200 nm, e.g., having an average particlesize of 2 nm, 5 nm, 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, which may beuniform or non-uniform with respect to anode active material particles110 in anode 100 and not necessarily corresponding to the size of anodeactive material particles 110 which carry layer 120. Layer 120 of borateand/or phosphate salt(s) 102A and/or of borate oxides (B₂O₃, and/orrelated salts) and/or phosphate oxides (P₂O₅, and/or related salts)formed therefrom of the surface of anode active material particles 110may be continuous or discontinuous (e.g., small B₂O₃ and/or P₂O₅crystals in the latter case) and may be coated by additional coating(s)120B—see e.g., FIG. 4C, with coating 120A possible indicating layer 120of borate and/or phosphate salt(s) 102A and/or of borate oxides (B₂O₃,and/or related salts) and/or phosphate oxides (P₂O₅, and/or relatedsalts).

In certain embodiments, borate and/or phosphate salt(s) 102A and/or ofborate oxides (B₂O₃, and/or related salts) and/or phosphate oxides(P₂O₅, and/or related salts) may be used to form modified anode activematerial particles 110A and configured to reduce or prevent aggregationof modified anode active material particles 110A, possibly utilizingsimilar mechanical effects as B₄C nanoparticles 112 described above.

Without being bound by theory, understood as part of modified anodeactive material particles 110A, borate and/or phosphate salt(s) 102A andprocesses 105 may be selected and/or configured to provide any of thefollowing effects. During expansion and contraction 101, formed borateoxides (B₂O₃, and/or related salts), LTB (lithium tetraborate) and/orphosphate oxides (P₂O₅, and/or related salts) may be pushed further intomodified anode material particles 110A, to provide internal mechanicalstabilization. Positioned mainly on the surface of modified anodematerial particles 110A, borate and/or phosphate salt(s) 102A may beselected to lower the surface potential of modified anode materialparticles 110A and reduce the rate modified anode material particles110A merge and agglomerate. Reduction of surface potential may alsoprovide better contact with electrolyte 85, improving ionic conductivityof the lithium ions into and out of modified anode material particles110A. Moreover, reducing agglomeration also increases the surface areaof modified anode material particles 110A which is available to lithiumions movements into and out of modified anode material particles 110A,and thereby increases the ionic conductivity and speed of charging anddischarging.

In certain embodiments, borate and/or phosphate salt(s) 102A attachedonto anode active material particles 110 may form at least a partialshell structure which allows expansion and contraction 101 of modifiedanode material particles 110A, as illustrated below concerning compositeanode material particles 115.

In certain embodiments, borate and/or phosphate salt(s) 102A andprocesses 105 may be selected and/or configured to reduce or removeoxides of the anode active material which may be present and/or mayevolve in anode 100 by forming compounds such as Li₂B₄O₇ (lithiumtetra-borate salt, e.g., via the reaction 4Li+7MeO+2B₂O₃→2Li₂B₄O₇+C+7Me(not balanced with respect to C and O, carbon originating fromadditives), with Me denoting active material such as Si, Ge, Sn, Aletc.), which have higher affinity to oxygen than the anode activematerial. Preventing oxidation not only increases the available activematerial surface area for lithiation but also helps preventmetallization of lithium on the surface of modified active materialparticles 110A (see above).

In certain embodiments, coatings 120, such as illustrated e.g., in FIGS.3C and 3D, may further enhance electronic and/or ionic conductivity. Forexample, thin films (e.g., 1-50 nm, or 2-10 nm thick) of carbon (e.g.,amorphous carbon, graphite, graphene, etc.) and/or transition metaloxide(s) (e.g., Al₂O₃, B₂O₃, TiO₂, ZrO₂, MnO etc.) may be added tomodified anode material particles 110A and/or their aggregates to formcomposite active material particles 115, as disclosed in additionalexamples below. Any of coatings 120 disclosed below may be applied ontomodified anode material particles 110A comprising borate and/orphosphate salt(s) 102A.

In certain embodiments, coating(s) 120 may be configured to provide gaps140 for expansion and contraction 101 and/or be flexible to allow forexpansion and contraction 101, as disclosed below (see e.g., FIGS. 8A,8D).

In certain embodiments, coating(s) 120 may be configured to support andstabilize a SEI (as illustrated schematically, e.g. in FIG. 2D),preventing cracks therein and preventing particles from merging into oneanother, thereby maintaining a large active material surface area.

In certain embodiments, borate and/or phosphate salt(s) 102A andprocesses 105 may be selected and/or configured to reduce potentialdecomposition of electrolyte solvent by carbon coating(s) 120, throughthe close proximity of borate and/or phosphate salt(s) 102A and coating120, which decreases its surface potential and the carbon's reactivitytowards the electrolyte solvent.

Coating(s) 120 of transition metal oxide(s) (e.g., Al₂O₃, B₂O₃, TiO₂,ZrO₂, MnO etc.) may further enhance mechanical stability of modifiedactive material particles 110A, and may be combined with othercoating(s) 120 disclosed below to form composite active materialparticles 115. Transition metal oxide coating(s) 120 may be furtherconfigured to provide buffering zone 110B and prevent lithiummetallization as described above, and possibly increase ionicconductivity of composite active material particles 115.

In certain embodiments, borate and/or phosphate salt(s) 102A andprocesses 105 may be selected and/or configured to prevent prior artdisadvantages of using transition metal oxide coating(s) 120, bystabilizing the SEI and preventing crack formation. Combining borateand/or phosphate salt(s) 102A and transition metal oxide coating(s) 120may provide an improved mechanical skeleton for composite activematerial particles 115 (e.g., a stable shell structure, as shown below)which provides sufficient mechanical support and maintains anodeperformance at high C rates, e.g., 2 C, 5 C, 10 C or possibly tens oreven a few hundred C.

In certain embodiments, borate and/or phosphate salt(s) 102A maycomplement and/or replace doping of anode active material particles 110with B and may achieve similar or complementary effects with respect toreduction of the surface potential and reactivity toward theelectrolyte.

Some embodiments may include ball milling, under protective atmosphere,anode active material particles 110 with nanoparticles 102A comprisingB₂O₃ and/or P₂O₅. For example, ball milling of oxo-borate salt withactive material nanoparticles (e.g. Li₂B₄O₇ and Ge). In someembodiments, the ball milled active material nanoparticles include tin,silicon, germanium, lead and/or their alloys). The ball milling mayenforce surface reaction and coating of the anode material with P₂O₅and/or B₂O₃ layer 120 (102A)—to yield a powder of modified anodematerial particles 110A and/or aggregate thereof which are coated withB₂O₃ and/or P₂O₅. Modified anode material particles 110A may be between20-500 nm (average diameter), and may be further milled in the presenceof carbon (e.g., graphite, graphene and the like) to form carbon coating120B and/or may be further milled in the presence of transition metaloxide (e.g., Al₂O₃, TiO₂, ZrO₂, MnO and the like) to form an oxidecoating 120B of the surface of modified anode material particles 110Acoated with B₂O₃ and/or P₂O₅ as layer 120A. Anode 100 may be formedtherefrom by processes 105 discussed above.

Composite Organic-Inorganic Coatings

FIG. 6 is a high level schematic illustration of composite coating 120comprising interconnected organic and inorganic compounds, according tosome embodiments of the invention. In the illustrated non-limitingexample, coating 120 may comprise a combination of lithium borates(e.g., Li₂B₄O₇) which anchor (180A) coating layer 120 to anode activematerial 110, and polymer molecules (180B) having electron rich groups(e.g., conjugated bonds, acidic groups, etc.) which provide, togetherwith lithium borates interconnecting the polymer molecules, ionicconductivity paths 103 through coating layer 120 and have an ionicconductivity which is much larger than electronic conductivity (e.g., byone or few orders of magnitude). It is noted that lithium borates andlithium phosphates 128 may in some embodiments be used similarly toLi₂B₄O₇, which is provided in FIG. 6 as a non-limiting example.

Either or both the lithium borate molecules (and/or borate and/orphosphate salts 128) and the polymer molecules may have electron richgroups and may be pre-lithiated. Surface molecules layer 120 maycomprise multiple polymer layers interconnected by lithium borates.Surface molecules layer 120 may effectively protect anode activematerial 110 from reacting and decomposing the solvent of electrolyte85. Surface molecules layer 120 may bond cations and/or anions of ionicliquid additive (see below) at its top layer 180C. In certainembodiments, coating layer 120 may comprise bonding molecules 180 (seebelow) comprising the lithium borates and/or the polymer moleculesconfigured to bind electrolyte compound to provide electrolyte-bufferingzone(s) during charging and discharging of cell 150, as described belowin more detail. The lithium borates may be replaced by other inorganiccompounds, such as lithium phosphates disclosed above such as any oflithium borates and/or phosphates 128 disclosed herein. The polymermolecules may comprise any of the polymers disclosed above, in operativeconfiguration.

Composite Particles

FIG. 7A is a high level schematic illustration of core-shell particle115 with composite shell 120 in composite anode material and itsadvantages, according to some embodiments of the invention—with respectto prior art 80 illustrated schematically in FIG. 7B. Core-shellparticle 115 may be implemented as composite anode material particles115 disclosed herein, with anode material particles 110 and/or 110A ascores and coating(s) 120 as shells.

As prior art brittle coating 83 of anode active material particles 81cracks upon expansion of lithiated particles 81A due to the mechanicalstrain, active material particles 81 lose coatings 83A after the firstcharging cycles. In contrast, core-shell particle 115 with compositeshells 120 made of brittle component 120A embedded in a flexiblecomponent 120B—maintain cracked brittle coating 120A (cracking may occurduring or after at least one charging and discharging cycle) at thevicinity of lithiated cores 110 (lithiation indicated schematically byLi^(˜01)) within flexible component 120B of shell 120. Moreover, brittlecomponent 120A is retained at the vicinity of cores 110 during furthercycles by flexible component 120B, and may at least partially adhere tocores 110.

Finally, brittle component 120A may be selected to be a good ionicconductor and thereby function as ionic conductive material 142(illustrated in FIG. 8D below) to provide ion paths or gates amongcore-shell particle 115 in anode 100, while flexible component 120B maybe selected to be a good electronic conductor and thereby function aselectronic conductive material 144 (illustrated in FIG. 8D below), asschematically required in FIG. 2B. For example, lithium titanate oxide(LTO) may be used as ionic conductive brittle component 120A andpolyaniline may be used as electronic conducting flexible component120B, forming conducting elastic shell 120 with high electronic andionic conductivity encapsulating anode active material particles 110 toform core-shell particles 115 as composite anode material. Flexiblecomponent 120B may be re-enforced with conductive fibers 130, at leastsome of which contact cores 110, as explained below.

In some embodiments, ionic conductive material 142 (FIG. 8D below) maybe at least partly embodied in brittle component 120A embedded in aflexible component 120B (FIG. 7A). For example, metalloid nanoparticles(as cores 110, or possibly cores made of other materials, listed above)may be coated by a TiO₂ precursor to form an amorphous TiO₂ and/orpossibly be calcined or annealed to form TiO₂ coating on the metalloidnanoparticles, such as cores 110. The TiO₂ may then undergo lithiationwith a lithium salt, followed by a second annealing (or calcination),e.g., in air or in an inert atmosphere, to form the lithium titanateoxide (LTO) coating 120A, which has fast anodic kinetics. The particlesmay be coated again by elastic and electronic conducting shell 120Bwhich may comprise a layered material and/or an organic polymer. Whenused as an electrode material in lithium ion batteries, metalloid cores110 expand, breaking up LTO layer 120A, fragments 120A of which becomingembedded in elastic shell 120B. As metalloid particle cores 110 expand,their surface presses up against LTO fragments 120A embedded in elasticshell 120B to form an ionic conducting bridge (as ionic conductivematerial 142) to encapsulated metalloid particle cores 110, whileelastic shell 120B maintains the electronic connection (as electronicconductive material 144) to cores 110. Advantageously, the suggestedprocedure results in composite anode material with core-shell particles115 that provide good ionic and electronic conductivity and ismechanically robust with respect to expansion and contraction 101 causedby lithiation and de-lithiation processes. It is noted that cores 110may be metalloid and/or be made of other materials, listed above.

In a specific, non-limiting example, metalloid nanoparticles (as cores110) were dispersed in ethanol solution. A metalorganic titaniumprecursor, e.g., titanium isopropoxide, was added as a precursor forTiO₂. The particles were coated in solution, using ammonium hydroxide asa catalyst. The product was calcined in air at 700° C. to form the TiO₂coating. The particles were again dispersed in ethanol and LiOH.2H₂O wasadded. The ethanol was evaporated and the particles were calcined againin air at 700° C. to form LTO-covered metalloid particles (having cores110 and brittle component 120A). The particles were dispersed in amixture of acidic water and ethanol along with aniline, and then anammonium persulfate acidic solution was added. After polyaniline wasformed a base was added until reaching pH of about 9. Particles 115(having cores 110, brittle component 120A and the polyaniline asflexible component 120B) were then dried and used to prepare a slurrywhich was coated on a current collector and used as an anode (seeprocess 105 in FIG. 1B). Alternatively or complementarily,polypyrrole-based flexible component 120B may be prepared, using pyrrolemonomers instead or in addition to the aniline monomers, and adjustingthe polymerization conditions. Elements from procedures for preparingconductive coatings may be incorporated in these embodiments as well.

In certain embodiments, with metalloid nanoparticles comprising Sn orany other material which may oxidize in the process disclosed above,formation of TiO₂ may be carried out at room temperature by dispersingthe nanoparticles (e.g., Si—Sn nanoparticles) in deionized water (DI)and adding them to a mixture of boric acid and (NH₄)₂TiF₆, which afterstirring and cleaning in DI, may be followed by lithiation andoptionally annealing in argon atmosphere to avoid oxidation.

FIG. 7C is a high level schematic illustration of composite anodematerial particles 115 with graphite shell 120, according to someembodiments of the invention. Composite anode material particles 115 maybe prepared by milling 105A of anode material particles 110 withgraphite particles 120 to form graphite layer, or shell 120 over anodematerial particles 110. An oxide layer 111 may cover at least part ofthe surface of anode material particles 110, and/or oxide layer 111 maybe at least partly removed, as taught in U.S. Pat. No. 9,406,927, whichis incorporated herein by reference in its entirety. In a non-limitingexample, Ge anode material particles 110 may be milled with 1-10% (ofthe overall weight) graphite particles 120, in a non-limiting examplewith 2-3% graphite particles 120 to yield graphite layer 120 1-5 nmthick over Ge anode material particles 110. Advantageously, graphitelayer 120 may provide several benefits such as reduction ofagglomeration of composite anode material particles 115 and reduction orprevention of contact between the electrolyte solvent and the anodematerial.

FIG. 7D is a high level schematic illustration of composite anodematerial particles 115 with porous graphite shell 120, according to someembodiments of the invention. Graphite particles 121A may be milled(105B) with carbohydrate particles 121B such as sugar crystals to yieldgraphite-sugar particles 121C (as a non-limiting example forgraphite-carbohydrate particles). Non-limiting examples may comprisemixing (105B) graphite 121A and sucrose 121B at 1:1 weight ratio, orbetween 3:7 and 8:2 weight ratios (respectively).

Graphite-sugar particles 121C may then be milled (105A) with anodematerial particles 110 to form graphite-sugar layer 121C over anodematerial particles 110, having native oxide layer 111 over at least partof the surface of anode material particles 110. Then, a carbonizationstep 105C is carried out to form porous graphite shell 120 and yieldde-oxidized anode material particles with composite porouscarbon-graphite coating 115. It is emphasized that illustrated process105B, 105A, 105C may be carried out in dry environment, avoidingagglomeration of composite anode material particles 115.

Carbonization step 105C may be carried out at 600-900° C. in neutralatmosphere (e.g., Ar, N, CO₂, and their mixtures) and be fine-tuned tocarry out simultaneously at least partial reduction of native oxidelayer 111 and evaporation of water and gasses from graphite-sugar layer121C to make graphite coating (or shell) 120 porous. For example,carbonization step 105C may be configured for any of the followingreactions to take place. First, carbonization of the carbohydratecomponent of graphite-sugar layer 121C occurs, namelyC_(m)(H₂O)_(n)→mC+nH₂O (e.g., for sucrose, C₁₂H₂₂O₁₁→12C+11H₂O),releasing water vapor and leaving behind carbon and pores in graphiteshell 120. Second, multiple reduction reactions remove at least part ofthe anode material native oxide, due to its interactions with carbon andCO released by the carbonization of the carbohydrates and interactionsof the water vapor with carbon (for example, in the non-limiting case ofGe with GeO₂, GeO₂+2C→Ge+2CO, GeO₂+2CO→Ge+2CO₂, GeO₂+2H₂→Ge+2H₂O, withH₂ formed by C+2H₂O→CO₂+2H₂ and so forth). Carbonization step 105C maybe configured to remove at least part of native oxide layer 111, providea predefined level of porosity in graphite shell 120 and strengthen thebinding of graphite shell 120 to anode material particle 110 by themultitude of reduction and other reactions occurring in carbonizationstep 105C.

Advantageously, de-oxidized anode material particles with porousgraphite coating 115 provide multiple advantages, both in anodeoperation aspects and with respect to anode preparation processes 105.

In anode 100, porous graphite shell 120 may enhance ionic conductivity,as lithium (e.g., Li⁺ and/or Li^(δ+)) may diffuse at least partlythrough the formed pores, while maintaining electronic conductivitythrough the graphite. Removal, or partial removal, of native oxide layer111 may further improve ionic and electronic conductivity. Moreover,porous graphite shell 120 may be configured to stabilize anode materialparticles 110 and possibly reduce their expansion 101 due to themechanical stability of porous graphite shell 120 and/or due to thestronger binding between anode material particles 110 and porousgraphite shell 120 which is formed during carbonization step 105C.Reduction of anode material expansion increases the mechanical stabilityof anode 100 and its cycle lifetime. Moreover, porous graphite shell 120may be configured to regulate the formation of SEI in an advantageousway such as on the surface of porous graphite shell 120 and away fromreactive anode material particles 110, thereby possibly reducing lithiumconsumption in the SEI, providing some flexibility to the formed SEI,and maintaining good ionic and/or electronic conductivity of compositeparticles 115. In certain embodiments, additional coatings such aspolymer coatings and/or lithiated coatings disclosed herein may beapplied on top of porous graphite shell 120 to further enhance any ofthese advantages and/or provide buffering zone(s) 110B. In certainembodiments, porous graphite shell 120 may be configured to provide atleast part of buffering zone(s) 110B.

With respect to anode preparation process 105, porous graphite shell 120may be configured to prevent aggregation of composite particles 115, inthe milling processes and particularly when processed in water-basedslurries, due to lower surface energy thereof. Advantageously, compositeparticles 115 with porous graphite shell 120 also exhibit lessaggregation in organic solvents, such as NMP (N-Methyl-2-pyrrolidone).Dry processes 105B, 105A, 105C provide fine powder composite particles115, which is beneficial for anode preparation process 105.

In any of the disclosed embodiments, electronic conductive materialand/or fibers 130 may extend to the surface of anode 100. Electronicconductive material 130 may comprise electronic conductive fibers and/ornon-fibrous electronic conductive material.

Cores 110 may comprise any of anode active material particles 110, 110Adisclosed above. Cores 110 may comprise alloy-type materials such as anyof single elements Sn, Si, Ge, Pb, P, Sb, Bi, Al, Ga, Zn, Ag, Mg, As,In, Cd and Au, and/or mixtures and/or alloys of these elements. In someembodiments, cores 110 may comprise any of the above materials, mixedwith a carbon matrix.

Various pre-coatings 120 and coatings 130 may be applied to core-shellparticles 115 and/or anode 100, e.g., at least partially filling gaps140, coating shells 120 and/or coating regions of anode 100. Example forvarious pre-coatings 120 and coatings 130 are disclosed above and may beimplemented in this context. Carbon-based material may be configured toform coatings 120 around cores 110 and/or cores 110 may be embedded incarbon matrix forming a composite structure. For example, carboncoatings may be applied in a thickness range of 5 nm to 5 μm, in aconcentration range of 5% to 95% of anode 100, and possibly be made ofsoft carbon, hard carbon and/or graphitic carbon. In certainembodiments, pre-coatings 120 and/or coatings materials 130 may beconfigured to provide at least part of the shell material of shells 120.

Conductive fibers 130 may comprise carbon-based material, such asspecifically designed fibers e.g., carbon fibers and/or carbonnanotubes, and/or carbon-based coating material which is modified intoconductive fibers 130 during preparation of anode 100. For example,conductive fibers 130 may comprise any of nanofibers structures CNT(carbon nanotubes), carbon fibers and/or graphene nano-sheets/platesstructures at an amount in a range of 0.0001%-15% with respect to thetotal anode material, possibly embedded, at least initially, in thecarbon-based coating.

In certain embodiments, anode 100 may comprise weight ranges of 50-95%active material, at least partly as core-shell particles 115, 1-40% ofconductive fibers 130 (e.g., as conductive agent material, possiblyincluding coating material) and 1-40% of binder material.

Advantageously, disclosed core-shell particles 115 and the compositeanode material enable use of metalloid (e.g., Si, Ge, Sn, mixturesand/or alloys thereof) particles (or cores made of other materials,listed above) as anode material, in spite of their lower electronicconductivity and larger mechanical expansion upon lithiation withrespect to graphite as anode material, and thereby enable takingadvantage of their remarkably high capacity. In particular, disclosedcore-shell particles 115 and composite anode material may be especiallyadvantageous for fast charging lithium ion cells, to accommodate themechanical stresses and maintain high electronic and ionicconductivities to metalloid cores 110 (or cores made of other materials,listed above).

Conductive Fibers and Core-Shell Particles

In various embodiments, the anode material of anode 100 may comprisecomposite anode material particles 115 which may be configured as coreshell particles, e.g., with anode material particles 110 and/or 110A ascores and coating(s) 120 or parts thereof as shells. Active materialparticles 110, possibly pre-coated 120 (in one or more layers 120, e.g.,by conductive polymers, lithium polymers, etc., B₂O₃, P₂O₅, etc.) andpossibly with various nanoparticles (e.g., B₄C, WC etc.) 112 attachedthereto, may provide at least part of cores 110 of core-shell particle115, while shell 120 may be at least partly be provided by coating(s)120, and may be configured to provide a gap 140 for anode activematerial 110 to expand 101 upon lithiation. In some embodiments, gap 140may be implemented by an elastic or plastic filling material and/or bythe flexibility of coating(s) 120 which may extend as anode activematerial cores 110 expand (101) and thereby effectively provide room forexpansion 101 (see e.g., high-level schematic illustration in FIG. 8D).

FIG. 8A is a high level schematic illustration of core-shell particle115, according to some embodiments of the invention. Core-shell particle115 comprises at least one core 110 and shell 120 which may be in directcontact and/or may be connected by electronic conductive material 130such as conductive fibers 130 (in non-limiting examples). One or morecores 110 are configured to receive and release lithium ions (Li⁺) inthe charging and discharging process, respectively, and shell 120 isconfigured to allow for, or accommodate core expansion 101 uponlithiation in core 110 (see also FIG. 2B). Core(s) 110 may be separatedfrom shell(s) 120 by gap(s) 140 which may be voids, gaseous or at leastpartly filled with compressible material such as a polymer material orother mechanically compliant material. In some embodiments, core(s) 110may be in direct contact with respective shell(s) 120, in some of thelithiation states of core(s) 110 and/or in some of core-shell particle115 in anode 100. Shell 120 is further configured to enable and/orfacilitate movement of lithium ions (indicated schematically in anon-limiting manner by arrow 103) to core(s) 110, e.g., have high ionicconductivity, while conductive fibers 130 are configured to conductelectrons (indicated schematically in a non-limiting manner by arrow106) from core(s) 110 to shell 120, e.g., have high electronicconductivity. It is noted that arrows 103, 106 denote lithium ion andelectron movement during charging of the respective lithium cell.Electronic conductive material 130 (such as conductive fibers 130) maybe configured to form a network throughout anode material 100(non-limiting examples for networks are illustrated in FIGS. 1B, 8A, 8Cand 8F) and possibly interconnect cores 110 of many core-shell particles115 to provide conduction pathways between particles 115 and enhance theelectronic conductivity of anode 100.

In certain embodiments, shell 120 may be made of an ionic conductivematerial having a high ionic conductivity only, without electronconductivity, e.g., from an insulating material, while the electronicconductivity is provided by electronic conductive material 130 (such asconductive fibers 130, e.g., carbon fibers or carbon nanotubes). Suchconfigurations may vastly improve upon prior art technology which wouldhave required shell material and structure to possess high conductivityfor both electrons and ions. The disclosed ability to provide theelectronic conductivity by electronic conductive material 130 opens up alarge variety of ionic conductors, including insulators, to be used asshell material for shells 120. Thus, in certain embodiments, shells 120are made of ionic conductors which are electronic insulators.

FIGS. 8B and 8C are high level schematic illustrations of compositeanode material 100 comprising a plurality of core-shell particles 115,according to some embodiments of the invention. As illustratedschematically in FIG. 8B, particles 115 and/or cores 110 may beinterconnected by conductive fibers 130, which may extend beyond shells120. As illustrated schematically in FIG. 8C, conductive fibers 130 mayextend over a plurality of core-shell particles 115, interconnectingtheir cores 110 along long distances of multiple particles 115.

For example, cores 110 may be made of SnSi, shells 120 may be made ofcarbon and conductive fibers 130 may comprise carbon nanotubes, e.g.,having diameters between 10-20 nm, and/or possibly up to diameters inthe order of magnitude of 100 nm and lengths between 3 μm and 100 μm,and/or possibly down to lengths in the order of magnitude of 100 nm. Forexample, conductive fibers 130 may be grown in a chemical vapordeposition (CVD) process, e.g., using cores 110 as seeds. Cores 110 maycomprise any of anode active material particles 110 and/or any of anodeactive material particles 110A disclosed above. Multiple types and/orsizes of core-shell particles 115 may be used in preparing anode 100.

FIG. 8D is a high level schematic illustration of a core-shell particle115, according to some embodiments of the invention. In certainembodiments, core(s) 110 and shell 120 of core-shell particle 115 may beconnected by ionic conductive material 142 (ionic conductivity indicatedschematically by arrow 103), by electronic conductive material 144(electronic conductivity indicated schematically by arrow 106, e.g.,conductive fibers 130), with mechanical elements or material (and/orgaps(s)) 140 between core(s) 110 and shell 120 being empty or havingcompliant material which allows for and/or accommodates mechanicalexpansion of core(s) 110 (indicated schematically by arrow 101) uponlithiation into core(s) 110. It is noted that arrows 103, 106 denotelithium ion and electron movement during charging of the respectivelithium cell.

FIG. 8E is a high level schematic illustration of composite anodematerial 100 comprising a plurality of core-shell particles 115,according to some embodiments of the invention. As illustratedschematically in FIG. 8E, at least some of shells 120 may comprisemultiple cores 110 which are interconnected by conductive fibers 130 andtogether form one or more layers of anode 100. Core-shell particles 115may extend to regions of anode 100 having assemblies of interconnectedcores 110 (interconnected by conductive fibers 130).

FIG. 8F is a high level schematic illustration of composite anodematerial 100, according to some embodiments of the invention. Compositeanode material 100 may comprise extended shell 120, possibly even singleshell 120 per anode layer, having a large plurality of cores 110,interconnected among themselves and with shell 120 by conductive fibers130.

Referring back to FIG. 7A it is noted that, in certain embodiments,shells 120 may comprise composite material, such as a brittle, ionicconductive component 120A embedded in a flexible, electronic conductivecomponent 120B, selected to accommodate swelling and contraction (101)of core 110 upon lithiation and de-lithiation, respectively. Forexample, the shell material may be coated onto cores 110 prior tolithiation and expand with core lithiation (at least during over or afew formation cycles, after which shell 120 may remain expanded).Referring back to FIG. 7D it is noted that, in certain embodiments,shells 120 may comprise porous graphite 120.

Preparation Processes

Examples for preparation stages 105 of the anode material may comprisemilling and/or mixing processes. In non-limiting examples, selectedanode material(s) may be milled e.g., in a high-energy ball-miller underprotective atmosphere or non-protective atmosphere to predefined averageparticle sizes, e.g., by milling the anode material(s) with graphitepowder and using hardened alumina media agitated at e.g., at least at650 RPM (revolutions per minute), possibly at 1000-1500 RPM, e.g., 1100RPM, 1200 RPM, 1300 RPM, 1500 RPM etc. for at least 45 hours, possiblyfor 48 hours, 55 hours, 60 hours or more.

Various additives such as B, W, nanoparticles 112 etc. may be introducedinto the ball milling process at specified stages thereof (for example,as WC or B₄C nanoparticles), to reach required particle sizes andaggregation levels, as disclosed herein. Various alloys may be formed inthe milling process, such as any combinations of Si, C, B and W alloys.

Specific non-limiting examples for anode compositions may comprise e.g.,(in weight percentage from the total weight of the anode): (i) 48% C,30% Si, 5.5% B, 8.3% binder and 8.2% conductive additives(C_(0.48)Si_(0.30)B_(0.055)Binder_(0.083)ConductiveAditive_(0.082)),with the as-milled C/Si/B alloy (active material particles) comprising57% C, 36% Si and 7% B weight percent of the total weight of the alloy(C_(0.57)Si_(0.36)B_(0.07)); (ii) 41.3% C, 30.1% Si, 11.6% W, 8.4%binder and 8.6% conductive additives(C_(0.413)Si_(0.301)W_(0.116)Binder_(0.084)ConductiveAditive_(0.086))with the as-milled C/Si/W alloy (active material particles) comprising50% C, 36% Si and 14% W in weight percentage of the total weight of thealloy (C_(0.50)Si_(0.36)W_(0.14)); (iii) 42% C, 30% Si, 5.0% B, 10.0% W,10% binder and 3% conductive additives(C_(0.42)Si_(0.3)B_(0.05)W_(0.1)Binder_(0.1) ConductiveAditive_(0.03)with the as-milled C/Si/B/W alloy (active material particles) comprising48.3% C, 34.5% Si, 5.7% B and 10.5% W in weight percentage of the totalweight of the alloy (C_(0.483)Si_(0.345)B_(0.057)W_(0.105)); (iv) 57% C,30% Si, 10% binder and 3% conductive additives(C_(0.57)Si_(0.3)Binder_(0.1) ConductiveAditive_(0.03)) with theas-milled C/Si alloy (active material particles) comprising 66% C and34% Si in weight percentage of the total weight of the alloy(C_(0.66)Si_(0.34)); (v) 69% Ge, 3% C, 10% W, 5% B, 10% binder and 3%conductive additives (Ge_(0.69)C_(0.03)W_(0.10)B_(0.080)Binder_(0.1)ConductiveAditive_(0.03)) with the as-milled Ge/C/W/B alloy (activematerial particles) comprising 79% Ge, 3% C, 12% W and 6% B weightpercent of the total weight of the alloy(Ge_(0.79)C_(0.03)W_(0.12)B_(0.06)).

In certain embodiments, oxide layers (e.g., GeO₂, SiO₂, Al₂O₃, SnO₂) onanode material particles 110 may be removed during preparation processes105 and possibly followed by application of protective coating(s),disclosed e.g., above, which prevent oxidation and maintain electronicand ionic conductivity. For example, removal of oxide layers(de-oxidation) may be carried out by heating particle mixture(s) in avacuum atmosphere, e.g., before or after ball milling steps. In anon-limiting example, de-oxidation may be carried out in a vacuumatmosphere of 10⁻³-10⁻⁶ mbar for 60-100 hours (removing formed gasessuch as CO) at a temperature of 150-350° C. Specific temperatures may beselected according to oxide bond strengths, e.g., for Ge a temperatureof 200° C. may be adequate to remove oxides without removing Ge; for Ala temperature between 400-600° C. may be adequate and for Sn to atemperature between 600-900° C. may be adequate remove oxides. Boratesand/or phosphates 128 may be introduced in the de-oxidation stage toform B₂O₃/P₂O₅ oxide layer(s) or nanocrystals to yield modified anodeactive material particles 110A as disclosed above.

In certain embodiments, binder or additives 102, as well as possiblycoatings 130, 120 may be selected to de-oxidize and/or contribute tode-oxidation of anode material particles 110. In certain embodiments,alumina may be removed from Al anode material particles 110 chemically,e.g., by immersing the aluminum particles in a dilute solution (forexample, 0.05M to 2M) of H₂SO₄ solution to form aluminum sulfate(Al₂O₃+3H₂SO₄ ⁻ →Al₂(SO₄)₃(aq)+3H₂O), which can then be used to bondvarious molecules or polymers as disclosed above, e.g., aqueous aluminumsulfate may be aggressively stirred with a lithium polymer to formcoating 120.

Examples for preparation stages 105 of coating(s) 120 may comprisepreparing lithium polymers by mixing 5 gr of PAA (polyacrylic acid)solution (25% wt) with LiOH solution and with 415 mg of LiOH powder(lithium hydroxide anhydrous), dissolved by adding 3.74 ml DI(distillated water) and stirring until clear solution is reached and/oruntil complete chemical reaction is achieved (e.g., overnight). Incertain embodiments, the pH of the resulting solution may be very basic,e.g., around 13. The Li-PAA solution may then be transferred intoevaporation glass according to the solution volume, evaporated inRotavapor evaporation glass which is then dried in an oven, e.g.,overnight at 120° C. The prepared Li-polymer may be placed in the ballmiller together with the anode material particles, which may possibly becoated with B₄C (e.g., any of particles 110, 110A, 115) and milledtogether. A non-limiting example for a ball milling method may include,milling 5% w/w lithium polymer powder with germanium (or with germaniumdoped with B₄C, and/or with Si, Sn, Al alloys and mixtures thereof,possibly doped with B and/or W) for 6 h at 200 rpm. Details of themilling process may be configured to cause the positively chargedlithium of the lithium polymer salt to favor the alloy anode materialand to react the alloy anode material surface to bind the negativelycharged anion of the polymer to the surface of particles 110, 110A, 115,leaving a partly charged entity chemically bound to coating 120.

Cell Configurations

Complementarily or alternatively, electronical properties of cell 150may be configured to optimize the dynamic charge/discharge and furtherreduce lithium ion accumulation at the interface. FIG. 9A-9C are highlevel schematic illustrations of cell configurations 150, according tosome embodiments of the invention, compared with prior artconfigurations 90 illustrated in FIG. 9D. In prior art designs 90, theresistance of cell elements to the movement of lithium ions is denotedR_(E) for the resistance of electrolyte 85, R_(S) for the resistance ofa cell separator 86, and R_(A) for the resistance of anode material 95,and generally these resistances are reduced to accommodate fastcharging. According to embodiments of the invention, cell configurations150, as illustrated e.g., in FIG. 9A, may comprise increasing aresistance r_(E) of a selected electrolyte 160 (and/or optionally aresistance r_(S) of a selected separator 152) to reduce the rate atwhich lithium ions reach anode material particles 110 (here and in thefollowing, referring optionally to modified anode material particles110A and/or to composite anode material particles 115). The increase maybe selected to maintain resistance r_(E) of electrolyte 160significantly lower than the resistance of anode 100 in order not toreduce the overall rate of lithium ion movement from cathode 87 to anode100, as the main limiting factor may be the lithiation rate of thelithium ions in anode material particles 110. For example, the inventorshave surprisingly found that electrolytes 160 with higher resistancer_(E)>R_(E) may be used in cells 150 to improve cell performance at highcharging rates. Moreover, as explained above, buffering zones 110B, 110Cin anode material particles 110 (shown schematically) may be configuredto regulate lithium ion lithiation process to be gradual, e.g., bydesigning anode 100 to have an initial resistance r_(A) and resistancesr″_(A), r′_(A) of buffering zones 110B, 110C, respectively, whichcontrol lithium ion movements into anode material particles 110 (e.g.,into the lithiation zone) according to the lithiation capacity of theanode material, to prevent lithium accumulation and metallization at theSEI. Clearly, resistance r_(E) of electrolyte 160 may be selected todiminish lithium ion accumulation at anode 100 to prevent metallizationbut not too large, in order to still enable fast charging of anode 100in cell 150. See also FIGS. 2A-2D above depicting ways to optimize theresistances in cell 150, in which buffering zone(s) 110B, 110C maycorrespond to buffering zone(s) 110B and/or coatings 120 illustratedtherein.

As illustrated schematically in FIGS. 9B and 9C, lithium ion cell 150may comprise modified anode 100 and modified electrolyte 160 comprisingup to 20%, up to 5%, and/or ca. 1% ionic liquid additive(s) which mayform a mobile SEI (e.g., in place of (static) SEI 122, in addition toSEI 122 or in an interaction with SEI 122, see FIG. 2D) on anodematerial particles 110, e.g., during charging, as illustrated in FIG. 9Band disclosed above. The ionic liquid additive(s) may comprisenitrogen-based ionic liquid(s) and may be selected to have a meltingtemperature below 10° C., below 0° C. or below −4° C., in certainembodiments (see examples below).

Layer 120 may be part of anode material particles 110 or coatedthereupon (see examples for bonding molecules 180 as part of coating120, below), and bind at least a part of the ionic liquid additive(s) tohold at least stationary portion 165A of the ionic liquid additive(s) atthe anode surface (FIG. 9C, leaving a mobile portion 165B of the ionicliquid additive(s) in electrolyte 160) to support the SEI, preventdecomposition of electrolyte 160 and prevent lithium metallization onanode 100. Layer 120 of bonding molecules 180 and/or layer 165A ofbonded ionic liquid additive may also provide some negative electriccharge that partly reduces the lithium ions, leaving them with a partialcharge δ⁺ and preventing full reduction and metallization of lithium onthe anode surface, providing, supporting and/or complementing gradient125 and/or the partial charge in buffering zone 110B (see FIGS. 2C,2E-2G). Layer 120 of bonding molecules 180 and/or layer 165A of bondedionic liquid additive may be configured to support an electric chargegradient 125 extending into electrolyte 160.

Bonding Molecules for Electrolyte-Based Buffering Zones

FIGS. 10A-10C and 11A-11C are high level schematic illustrations ofelectrolyte-based buffering zone(s) 165 which may be used in place or inaddition to anode-based buffering zone(s) 110B disclosed above,according to some embodiments of the invention. Coating 120 may beconfigured to support and stabilize disclosed electrolyte-basedbuffering zones 165 during charging and/or discharging of cells 150, andfurther enhance battery safety by preventing metallization, preventinginteraction between electrolyte solvents and the anode material, andpossibly improving the operation of the lithium ion batteries byincreasing the reversibility of lithiation and/or increasing thecoulombic efficiency of cells 150. The following disclosure relates toanode active material particles 110 in a non-limiting manner, and may beequally applied in some embodiments to modified anode active materialparticles 110A and/or to composite anode active material particles 115as described above.

In certain embodiments, electrolyte 85 may be replaced or modified intoan electrolyte 160 which comprises one or more ionic liquid additive 163having at least one type of cation 162 and at least one kind of anion161. For example, ionic liquid additive(s) 163 may comprisenitrogen-based ionic liquids and their combinations:1-butyl-1-methylpyrrolidinium as cation 162 andbis(trifluoromethanesulfonyl)imide as anion 161;1-butyl-6-methylimidazolium as cation 162 andbis(trifluoromethanesulfonyl)imide as anion 161;1-butyl-6-methylimidazolium as cation 162 and bis(fluorosulfonyl)imideas anion 161; N,N-Diethyl-N-methyl-N-propylammonium as cation 162 andbis(fluorosulfonyl)imide as anion 161; and N-propyl-N-methylpiperidiniumas cation 162 and bis(trifluoromethanesulfonyl)imide as anion 161.Certain embodiments comprise nitrogen-based ionic liquids which arederived from these combinations, e.g., having various substituents. Incertain embodiments, ionic liquid additive(s) 163 may be configured foruse at room temperature, have a negligible vapor pressure, a wideelectrochemical potential window (e.g., up to 5.0 V in nitrogen-basedionic liquids), and structural stability across a large temperaturerange (e.g., down to any of 20° C., 10° C., 0° C. or lower, and up toone or several hundred ° C.). Ionic liquid additive(s) 163 maycontribute to formation of at least one electrolyte-buffering zone 165in electrolyte 160, at the interface of electrolyte 160 and anodematerial 110 and/or coating 120, which further prevents contact betweenthe solvent(s) of the electrolyte and reactive anode material 110, whilemaintaining required lithium ion conductivity between electrolyte 160and anode material 110. In certain embodiments, coating 120 may comprisebonding molecules 180 which bind at least some of cations 162 and/oranions 161 of ionic liquid additive(s) 163 to stabilizeelectrolyte-buffering zone(s) 165 during charging and discharging ofcell 150. Non-limiting examples for bonding molecules 180 are providedbelow.

In certain embodiments, coating layer 120 may comprise bonding molecules180 in a structure as illustrated in FIG. 6, configured to bind at leastsome of cations 162 and/or anions 161 of ionic liquid additive(s) 163 tostabilize electrolyte-buffering zone(s) 165 during charging anddischarging of cell 150.

FIG. 10A schematically illustrates at least one electrolyte-bufferingzone 165 in an electrolyte 160, according to some embodiments of theinvention. Electrolyte-buffering zone(s) 165 is illustratedschematically as an accumulation of anions 161 and cations 162, whichprovides additional separation between electrolyte 160 and anode activematerial particles 110 and may be configured to further regulate lithiumion movement between electrolyte 160 and anode active material particles110. For example, anions 161 and/or cations 162 may be relatively large,e.g., larger than lithium ions 91 and/or significantly larger thanlithium ions 91 to establish a gradient in physical and/or chemicalcharacteristics in region 165 and possibly provide an interphasetransition between electrolyte 160 and anode active material particles110 that enhances the stabilization of transition region and preventslithium ion accumulation and/or metallization and dendrite growth.Anions 161 may be selected to provide negative electric charge in theregion of lithium ions 91 moving towards anode active material particles110, which somewhat, yet not fully, reduces the positive charge oflithium ions 91 to δ+ (e.g., by physical proximity and not by a chemicalbond).

In certain embodiments, electrolyte 160 may comprise an ionic liquidadditive 163 added to prior art electrolyte 85 (e.g., at 20%, 10%, 5% orany other volume part of electrolyte 160), which is selected to at leastpartially provide anions 161 and/or cations 162 to buildelectrolyte-buffering zone(s) 165. For example, ionic liquid additive163 may comprise acidic groups which are selected to be anionic in theenvironment of lithium ions 91. Anions 161 and/or cations 162 may berelatively large to form a barrier which reduces the approaching speedof lithium ions 91 and locally increases the resistance of bufferingzone(s) 165 to lithium ions 91 to prevent or attenuate accumulation oflithium ions 91 at the surface of anode active material particles 110(see e.g., r_(A) in FIG. 9A) and/or achieve any of the effects disclosedbelow.

FIG. 10B schematically illustrates at least one electrolyte-bufferingzone 165 (MSEI) in an electrolyte 160, which is configured to provide amobility and charge gradient 125 (indicated schematically by the taperedarrows) having surrounding electric charge 126 (illustratedschematically as a non-specific symbol), according to some embodimentsof the invention. Mobility and charge gradient 125 reduces and slowslithium ions 91 entering zone 165 in a gradual manner (indicatedschematically by Li^(δ+), with the partial charge of the lithium ionschanging gradually within zone 165) until they reach lithiation in theanode active material. Gradient 125 enables modification of theinterface (the area where the two immiscible phase surfaces of anode andelectrolyte come into contact with each other) into an interphase region165 having a gradual change of parameters which gradually reduces theactivation energy of the reduction reaction of the lithium ions, andfurther prevents metallization of lithium and dendrite growth. MSEI zone165 helps smoothen the lithium ion transport into the active materialfor full reduction and intercalation (to Li^(˜01)). The resulting ionicliquid layer 165 reduces the probability of both lithium metallizationand de-composition of the organic solvent (electrolyte 85) at themetalloid-lithium surface. Once the electrical field stops (e.g., at theend or interruption of the charging), ionic liquid 163 may slowlydiffuse to form homogenous electrolyte 160. It is explicitly noted,however, that ionic liquid additive 163 may be used in cells havingmetalloid-based and/or graphite-based anodes (either option possiblycoated and/or pre-coated).

FIG. 10C schematically illustrates at least one electrolyte-bufferingzone 165 (MSEI) in an electrolyte 160, according to some embodiments ofthe invention. Electrolyte-buffering zone(s) 165 may be configured tofill in possible cracks 124 appearing in composite anode materialparticles 115, e.g., due to cracking of any of coating 120, anodebuffering zone 110B, or SEI layer 122 (see FIGS. 2B-2F) upon expansionand contraction 101 of anode material particles 110.

Filling cracks 124 may prevent renewed contact between the anode activematerial and/or metal lithium and electrolyte 85 due to exposure of theanode active material (e.g., when coating 120 is cracked) or due to theincrease in the surface area available for such contact due to cracks124. Electrolyte-buffering zone(s) 165 thus prevent further electrolytedecomposition, prevent further SEI growth and thickening, and blockpossible sites for lithium metallization from solvents of electrolyte85. Ionic liquid additive 163 may be configured to fill in such cracks124 (illustrated schematically in FIG. 10C) once an electric field isapplied, or possibly also after the electric field is applied, to reducethe extent of, or prevent, cracks 124 from enhancing electrolytedecomposition and lithium metallization. Ionic liquid additive 163 maybe configured to fill in cracks or uncoated surface areas as explainedabove, including possible exposed surfaces in the coating resulting fromexpansion and contraction 101 during cell cycles. Bonding molecules 180of any of the disclosed types may be incorporated in coating(s) 120and/or in coating(s) 130 and be configured to be present in cracks 124to bond with cations 162 and/or anions 161 of ionic liquid additive 163and achieve the crack filling and anode active material protectiondescribed above.

FIG. 11A is a high level schematic illustration of bonding molecules 180forming a surface molecules layer 120C at least as part of coating 120on anode 100 and/or on anode active material particles 110, according tosome embodiments of the invention. It is emphasized that FIG. 11A ishighly schematic and represents principles for selecting bondingmolecules 180, according to some embodiments of the invention. Actualbonding molecules 180 may be selected according to requirements, e.g.,from bonding molecules 180 represented by any one of formulas I-VII(detailed below), under any of their embodiments. The surface moleculeslayer may be part of coating 120 and/or associate or bonded thereto.

Surface molecules layer 120C may be configured to prevent contact ofelectrolyte solvent (of electrolyte 85) with anode active material 110,e.g., through steric hindrance by molecules 180. Non-limiting examplesare embodiments represented e.g., by formulas II, IV and V, amongothers, such as the non-limiting examples lithium3,5-dicarboxybenzenesulfonate, lithium2,6-di-tert-butylbenzene-1,4-disulfonate,3,3′-((1,2-dithiane-4,5-diyl)bis(oxy))bis(N-hydroxypropanamide),3,3′-((4-mercapto-1,2-phenylene)bis(oxy))bis(N-hydroxypropanamide), etc.

Molecules 180 may be selected and attached onto anode active material110 in a way that forms a mechanical and/or electrostatic barriertowards electrolyte solvent and prevents it from reaching andinteracting with anode active material 110. Bonding molecules 180 may beselected to have electron rich groups that provide mobile electriccharge on the surface of molecules layer 120C. Non-limiting examples areembodiments represented e.g., by formulas II, and IV-VII, havingconjugated double bonds, acidic groups and benzene groups, among others,such as the non-limiting examples lithium 4-methylbenzenesulfonate,lithium 3,5-dicarboxybenzenesulfonate, lithium2,6-dimethylbenzene-1,4-disulfonate,3,3′-((1,2-dithiane-4,5-diyl)bis(oxy))bis(N-hydroxypropanamide),3,3′-((4-mercapto-1,2-phenylene)bis(oxy))bis(N hydroxypropanamide),lithium aniline sulfonate, poly(lithium-4-styrenesulfonate) etc.

For example, bonding molecules 180 may be selected to have a width W(anchored in anode 100 and/or anode active material particles 110) of upto three benzene rings and a length L (protruding into electrolyte 160)of up to four benzene rings, as exemplified in a non-limiting manner inembodiments represented e.g., by formulas II and VII having bicyclic ortricyclic structures, e.g., anthracene-based structures and/or inembodiments represented e.g., by formulas IV and V.

In some embodiments, bonding molecules 180 may comprise an anodematerial anchoring part 180A, configured to bind to or be associatedwith anode active material 110, e.g., via lithium, thiols, or otherfunctional groups in bonding molecules 180. In some embodiments, anodematerial anchoring part 180A may be pre-lithiated exemplified in anon-limiting manner in embodiments represented by any of formulas I-VIIwhich include lithium, such as the non-limiting examples illustrated inFIG. 11D. FIG. 11D is a high level schematic illustration ofnon-limiting examples for bonding molecules 180, according to someembodiments of the invention.

In some embodiments, bonding molecules 180 may comprise an ionicconductive part 180B having an ionic conductivity which is much higherthan its electronic conductivity, e.g., by one, two, three or moreorders of magnitude. Ionic conductive part 180B may extend through mostor all of length L of bonding molecules 180 and provide a conductivitypath 103 (illustrated schematically) for lithium ions 91 moving back andforth between electrolyte 160 and anode 110 during charging anddischarging cycles. Conductivity paths 103 may be provided e.g., byconjugated double bonds, acidic groups, benzene rings, carbon-fluorinebonds, charged functional groups etc. which are disclosed above. Forexample, the charge distribution on bonding molecules 180 may beselected to be mobile and support lithium ion movement across moleculeslayer 120C, possibly reducing the charge of the lithium ion to Li^(δ+)as explained above, to prevent metallization on the surface of anode110. Partial charge reduction may be carried out by electron rich groupssuch as aromatic groups and acidic groups disclosed above.

In some embodiments, bonding molecules 180 may comprise a top, ionicliquid binding part 180C configured to bind cations 162 and/or anions161 of ionic liquid additive 163 in electrolyte 160. For example,embodiments represented by any of formulas I-VII which involve chargedand/or polar functional groups may provide top, ionic liquid bindingpart 180C, e.g., lithium 3,5-dicarboxybenzenesulfonate, lithium sulfate,lithium phosphate, lithium phosphate monobasic, lithiumtrifluoromethanesulfonate, lithium1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluorooctane-1-sulfonate,lithium 2,6-dimethylbenzene-1,4-disulfonate, lithium2,6-di-tert-butylbenzene-1,4-disulfonate,3,3′-((1,2-dithiane-4,5-diyl)bis(oxy))bis(N-hydroxypropanamide),3,3′-((4-mercapto-1,2-phenylene)bis(oxy))bis(N-hydroxypropanamide),lithium aniline sulfonate (the sulfonate may be in any of para, meta andortho positions) as well as poly(lithium-4-styrenesulfonate), as somenon-limiting examples. Ionic liquid binding part 180C may be furtherconfigured to stabilize electrolyte-buffering zone(s) 165 as describedabove.

FIGS. 11B and 11C are high level schematic illustrations of animmobilized/mobilized SEI (I/MSEI) during charging and discharging,according to some embodiments of the invention. In certain embodiments,surface functionalization of the anode active material may enhance thefunctionality of MSEI 165, e.g., by increasing the affinity of ionicliquid additive 163 to the active material-electrolyte interface, andprotecting the interface further more from direct interaction with theorganic solvent (of electrolyte 85). Surface functionalization may beapplied by anode coatings 130 and/or by anode material particlepre-coatings 120 and/or by additional modifications of the surface ofanode 100 (e.g., of anode material particles 110) and/or of the activematerial on the anode surface. For example, chemically bonded layer 120Cof bonding molecules 180 (possibly as part of coating 120) such as largevolume salt(s) on the active material surface may be used to keep someof ionic liquid 163 on the surface and reduce the probability of theorganic solvent de-composition prior to the MSEI re-arrangement at theinterface. FIGS. 11B and 11C schematically illustrate this effect by theretainment of at least some of cations 162 bonded to the surface evenwhen cell 150 is not charged. FIGS. 11B and 11C schematically illustrateanode material particles 110 during charging and discharging (or nocharging) with ionic liquid additive 163 building MSEI 165 in thecharging state, which may comprise an immobilized section 165A and amobile section 165B, the former remaining in the discharging state,bonded or associated with anode surface while the latter return intoelectrolyte 160 in the discharging state. Coating 120 may comprise layer120C in which bonding molecules 180 are associated with anode materialparticle coating 120 and/or attached to anode 100, possibly as coating130. Cations 162C and possibly anions 161C which stay bonded to bondingmolecules 180 (immobilized section 165A of ionic liquid additive 163)are denoted differently from cations 162B and anions 161B which stay inelectrolyte 160 (mobile section 165B of ionic liquid additive 163), toillustrate that a part (or possibly all) of electrolyte additive 163 isimmobilized onto layer 120C of anode material particle 110 duringoperation of cell 150. Immobilized layer 165A at the interface may havea better affinity to ionic liquid 163 and less affinity toward organicsolvent of electrolyte 85, and therefore keep the organic solvent awayfrom the interface and reduce the probability for its de-composition.

In some embodiments, the bonding of ions of ionic liquid additive(s) 163may involve bonding cations 162 or possibly anions 161 by bondingmolecules 180 as the layer closest to the surface of anode activematerial particles 110. The bonding may be carried out during one ormore first charging and discharging cycles of cell 150. In certainembodiments, the bonding of cations 162 and/or anions 161 may be carriedout, at least partially, on active material particles 110 themselves,even before the first charging cycle. The bonding of ionic liquidadditive 163 to bonding layer 120C of coating 120 may be electrostaticand/or salt-like (ionic). In certain embodiments, the bonding may be atleast partly covalent. The bonding may involve any number of ioniclayers, typically a few layers, possibly providing a salt layer whichisolates the organic solvent used for electrolyte 85 at least fromactive material 110 of anode 100.

Bonding molecules 180 may be ionic or have electron rich groups such assodium aniline sulfonate. Bonding molecules 180 may comprise lithiumcations and/or possibly magnesium cations, the latter possibly when theanode material is graphite. In case of aluminum as anode material,bonding molecules 180 may comprise lithium cations and/or aluminumcations. The lithium in the following examples may thus be replaced insome embodiments by magnesium and/or aluminum. In case of graphiteanodes, a wide range of activation techniques which yield oxidizedgraphite may be used to enhance chemical bonding of molecules 180 (e.g.,using halides or alkoxides).

Non-limiting examples for bonding molecules 180 comprise lithiumalkylsulfonate, poly(lithium alkylsulfonate), lithium sulfate, lithiumphosphate, lithium phosphate monobasic, alkylhydroxamate salts and theiracidic forms (e.g., lithium sulfonic acid, LiHSO₄, instead of lithiumsulfonate, Li₂SO₄). The chemical bonding of molecules 180 to anode 100(e.g., to anode material particles 110) may be carried out, for example,in the anode slurry solution and/or in dry ball milling with anodematerial particles (in process 105). The bonding mechanism may comprise,e.g., reaction(s) of the lithium sulfonates and/or salts with metaloxides, releasing the oxide and creating a direct chemical bond to theanode material (e.g., Si, Ge, Sn, Al, mixture and alloys thereof)surface of anode material particles 110, where the lithium cation remainpartly charged (Li^(δ+)) in the anode material. For example, using alarge volume salt with an additional anion group as bonding molecules180 may create a salt surface 120C on anode active material particles110, which can both protect the interface and co-operate with ionicliquid additive 163 in electrolyte 160. Layer 120C may bind a stationaryportion of ionic liquid additive 163 on the surface of anode activematerial particles 110 while the rest of ionic liquid additive 163 ismobilized in electrolyte 160, providing a hybrid ionic liquid additivewhich is partly bonded and partly free in electrolyte 160. Stationaryportion 165A may increase the re-ordering rate of ionic liquid additive163 on the surface during charging, help repel organic electrolyte 85from the interface and hence reduce the probability for thede-composition of the organic solvent. Non-limiting examples for bondingmolecules 180 include large anionic salts or their acids which may beselected to sterically repel the smaller organic carbonates solvents (ofelectrolyte 85) from the active material surface. Layer 120C andstationary portion 165A of ionic liquid additive 163 on surface of anodeactive material particles 110 may be highly effective during the initialcharging, and enable or support the building of a stable SEI during theformation cycle(s) which protects the surface of anode active materialparticles 110 and of anode 100 during later operation, and preventdecomposition of electrolyte on anode 100 as well as lithiummetallization thereupon.

The resulting SEI may be modified toward enhanced stability and bepossibly provided with self-healing mechanisms through layer 120C andstationary portion 165A of ionic liquid additive 163.

Non-limiting examples for bonding molecules 180 include any of thefollowing, illustrated below: lithium 4-methylbenzenesulfonate, lithium3,5-dicarboxybenzenesulfonate, lithium sulfate, lithium phosphate,lithium phosphate monobasic, lithium trifluoromethanesulfonate, lithium4-dodecylbenzenesulfonate, lithium propane-1-sulfonate, lithium1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluorooctane-1-sulfonate,lithium 2,6-dimethylbenzene-1,4-disulfonate, lithium2,6-di-tert-butylbenzene-1,4-disulfonate,3,3′-((1,2-dithiane-4,5-diyl)bis(oxy))bis(N-hydroxypropanamide),3,3′-((4-mercapto-1,2-phenylene)bis(oxy))bis(N-hydroxypropanamide),lithium aniline sulfonate (the sulfonate may be in any of para, meta andortho positions) as well as poly(lithium-4-styrenesulfonate) applied incoating the anode material particles as disclosed herein. It is notedthat in cases of coatings that contain lithium (e.g., metallic lithium),ionic liquid additive(s) 163 may be selected to be non-reactive towardit.

For example, various coatings of the anode active material may be usedto bond or enhance bonding of molecules 180 to anode material 110, asdisclosed above. The size(s) of molecules 180 may be selected to providegood lithium ion conductivity therethrough. In certain embodiments,molecules 180 may be selected (e.g., some of the disclosed salts) toform channels configured to enable fast lithium ion movementtherethrough.

In a more generalized sense, bonding molecules 180 may be selected fromany of the following sets of molecules, according to Formulas I-IV.

In some embodiments, surface layer 120C may comprise bonding molecules180 represented by the structure of formula I:

wherein:each Z is independently selected from aryl, heterocycloalkyl, crownetheryl, cyclamyl, cyclenyl, 1,4,7-Triazacyclononanyl, hexacyclenyl,cryptandyl, naphtalenyl, anthracenyl, phenantrenyl, tetracenyl,chrysenyl, triphenylenyl pyrenyl and pentacenyl;R¹ is [C(L¹)₂]_(q) ¹-R¹⁰¹;each L¹ is independently selected from H, F and R¹⁰¹;R², R³, R⁴, R⁵, R⁶ and R¹⁰¹ are each independently selected from CO₂H,CO₂M¹, CO₂R, SO₃H, SO₃M¹, PO³H₂, PO₃M¹ ₂, PO₃M¹H, PO₄H₂, PO₄M¹ ₂,PO₄M¹H, PO₄M², C(O)NHOH, NH₂, NHR, N(R)₂, NO₂, COOR, CHO, CH₂OH, OH, OR,SH, SR, C(O)N(R)₂, C(O)NHR, C(O)NH₂, halide, tosylate, mesylate, SO₂NHR,triflate, isocyanate, cyanate, thiocyanate, isothiocyanate, R, cyano,CF₃, and Si(OR)₃;each R is independently selected from methyl, ethyl, isopropyl,n-propyl, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, andbenzyl;each M¹ is independently Li, Na, K, Rb or Cs;each M² is independently Be, Mg, Ca, Sr or Ba;T¹ and T² are each independently absent, or selected from H, CO₂H,CO₂M¹, CO₂R, SO₃H, SO₃M¹, PO₃H₂, PO₃M¹ ₂, PO₃M¹H, PO₄H₂, PO₄M¹ ₂,PO₄M¹H, PO₄M², C(O)NHOH, NH₂, NHR, N(R)₂, NO₂, COOR, CHO, CH₂OH, OH, OR,SH, SR, C(O)N(R)₂, C(O)NHR, C(O)NH₂, halide, tosylate, mesylate, SO₂NHR,triflate, isocyanate, cyanate, thiocyanate, isothiocyanate, R, cyano,CF₃, and Si(OR)₃;m¹, m², m³, m⁴, m⁵, and m⁶ are each independently an integer between0-6;n¹ is an integer between 1-10;q¹ is an integer between 0-10; andZ is connected to any of R¹-R⁶, T¹-T² or to any neighboring repeatingunit in any possible substitution position and via one or more atoms.

In some embodiments, surface layer 120C may comprise bonding molecules180 represented by the structure of formula II:

wherein:R⁷ is [C(L²)₂]_(q) ²-R¹⁰²;each L² is independently selected from H, F and R¹⁰²;R⁸, R⁹, R¹⁰, R¹¹, R¹² and R¹⁰² are each independently selected fromCO₂H, CO₂M¹, CO₂R, SO₃H, SO₃M¹, PO₃H₂, PO₃M¹ ₂, PO₃M¹H, PO₄H₂, PO₄M¹ ₂,PO₄M¹H, PO₄M², C(O)NHOH, NH₂, NHR, N(R)₂, NO₂, COOR, CHO, CH₂OH, OH, OR,SH, SR, C(O)N(R)₂, C(O)NHR, C(O)NH₂, halide, tosylate, mesylate, SO₂NHR,triflate, isocyanate, cyanate, thiocyanate, isothiocyanate, R, cyano andSi(OR)₃;each R is independently selected from methyl, ethyl, isopropyl,n-propyl, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, andbenzyl;each M¹ is independently Li, Na, K, Rb or Cs;each M² is independently Be, Mg, Ca, Sr or Ba;m⁷, m⁸, m⁹, m¹⁰, m¹¹ and m¹² are each independently an integer between0-6; andq² is an integer between 0-10.

In some embodiments, surface layer 120C may comprise bonding molecules180 represented by the structure formula III:

(L₃)₃C—R¹⁰³   (III)

wherein:R¹⁰³ is [C(L⁴)₂]_(q) ³-R¹⁰⁵;each L³ is independently selected from H, F and R¹⁰⁴;each L⁴ is independently selected from H, F and R¹⁰⁶;R¹⁰⁴, R¹⁰⁵, and R¹⁰⁶ are each independently selected from CO₂H, CO₂M¹,CO₂R, SO₃H, SO₃M¹, PO³H₂, PO₃M¹ ₂. PO₃M¹H, PO₄H₂, PO₄M¹ ₂, PO₄M¹H,PO₄M², C(O)NHOH, NH₂, NHR, N(R)₂, NO₂, COOR, CHO, CH₂OH, OH, OR, SH, SR,C(O)N(R)₂, C(O)NHR, C(O)NH₂, halide, tosylate, mesylate, SO₂NHR,triflate, isocyanate, cyanate, thiocyanate, isothiocyanate, R, cyano,CF₃ and Si(OR)₃;each R is independently selected from methyl, ethyl, isopropyl,n-propyl, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, orbenzyl;each M¹ is independently Li, Na, K, Rb or Cs;each M² is independently Be, Mg, Ca, Sr or Ba; andq³ is an integer between 0-10.

In some embodiments, surface layer 120C may comprise bonding molecules180 represented by the structure of formula IV:

wherein:X¹ and X² are each independently selected from S, O and CH₂;R¹³ and R¹⁴ are each independently selected from CO₂H, CO₂M¹, CO₂R,SO₃H, SO₃M¹, PO₃H₂, PO₃M¹ ₂. PO₃M¹H, PO₄H₂, PO₄M¹ ₂, PO₄M¹H, PO₄M²,C(O)NHOH, NH₂, NHR, N(R)₂, NO₂, COOR, CHO, CH₂OH, OH, OR, SH, SR,C(O)N(R)₂, C(O)NHR, C(O)NH₂, halide, tosylate, mesylate, SO₂NHR,triflate, isocyanate, cyanate, thiocyanate, isothiocyanate, R, cyano,CF₃ and Si(OR)₃;each M¹ is independently Li, Na, K, Rb or Cs;each M² is independently Be, Mg, Ca, Sr or Ba;each R is independently selected from methyl, ethyl, isopropyl,n-propyl, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, orbenzyl; andn², n³, n⁴ and n⁵ are each independently an integer between 0-10.

In some embodiments, surface layer 120C may comprise bonding molecules180 represented by the structure of formula V:

wherein:X³ and X⁴ are each independently selected from S, O and CH₂;R¹⁵ and R¹⁶ are each independently selected from CO₂H, CO₂M¹, CO₂R,SO₃H, SO₃M¹, PO₃H₂, PO₃M¹ ₂. PO₃M¹H, PO₄H₂, PO₄M¹ ₂, PO₄M¹H, PO₄M²,C(O)NHOH, NH₂, NHR, N(R)₂, NO₂, COOR, CHO, CH₂OH, OH, OR, SH, SR,C(O)N(R)₂, C(O)NHR, C(O)NH₂, halide, tosylate, mesylate, SO₂NHR,triflate, isocyanate, cyanate, thiocyanate, isothiocyanate, R, cyano,CF₃ and Si(OR)₃;each M¹ is independently Li, Na, K, Rb or Cs;each M² is independently Be, Mg, Ca, Sr or Ba;each R is independently selected from methyl, ethyl, isopropyl,n-propyl, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, orbenzyl; andn⁶, and n⁷ are each independently an integer between 0-10.

In some embodiments, surface layer 120C may comprise bonding molecules180 represented by the structure of formula VI:

wherein:each R¹⁷ is independently selected from CO₂H, CO₂M¹, CO₂R, SO₃H, SO₃M¹,PO₃H₂, PO₃M¹ ₂. PO₃M¹H, PO₄H₂, PO₄M¹ ₂, PO₄M¹H, PO₄M², C(O)NHOH, NH₂,NHR, N(R)₂, NO₂, COOR, CHO, CH₂OH, OH, OR, SH, SR, C(O)N(R)₂, C(O)NHR,C(O)NH₂, halide, tosylate, mesylate, SO₂NHR, triflate, isocyanate,cyanate, thiocyanate, isothiocyanate, R, cyano, CF₃ and Si(OR)₃;T³ and T⁴ are each independently selected from H, CO₂H, CO₂M¹, CO₂R,SO₃H, SO₃M¹, PO₃H₂, PO₃M¹ ₂. PO₃M¹H, PO₄H₂, PO₄M¹ ₂, PO₄M¹H, PO₄M²,C(O)NHOH, NH₂, NHR, N(R)₂, NO₂, COOR, CHO, CH₂OH, OH, OR, SH, SR,C(O)N(R)₂, C(O)NHR, C(O)NH₂, halide, tosylate, mesylate, SO₂NHR,triflate, isocyanate, cyanate, thiocyanate, isothiocyanate, R, cyano,CF₃ and Si(OR)₃;each M¹ is independently Li, Na, K, Rb or Cs;each M² is independently Be, Mg, Ca, Sr or Ba;each R is independently selected from methyl, ethyl, isopropyl,n-propyl, alkyl, haloalkyl, cycloalkyl, heterocycloalkyl, aryl, orbenzyl; andn⁸ is an integer between 2-10000.

It is explicitly noted that bonding molecules 180 may be combined withany of the disclosed anode materials and/or with any of the disclosedcoatings, and possibly provide at least one coating layer 120, possiblyin connection with any of the disclosed polymers (e.g., the lithiumpolymers).

Methods

FIG. 12 is a high level flowchart illustrating a method 200, accordingto some embodiments of the invention. The method stages may be carriedout with respect to the anode and cell configurations described above,which may optionally be configured to implement method 200. Method 200may comprise stages for producing, preparing and/or using cells andanodes, such as any of the following stages, irrespective of theirorder.

Method 200 comprises increasing cell capacity and enabling fast chargingby using as anode active material any of Si, Ge, Sn, Al, alloys andmixtures thereof (stage 202) and/or configuring the anode to buffer theinterface reaction, zone the electrode to graduate Li⁺ ion lithiationand/or provide graduated resistance of the anode to the Li⁺ ions (stage205). Any of these configuration options may be provided separately orin combination, and be implemented by any of the active materials,modifications and coatings provided above. For example, method 200 maycomprise creating the buffering zone(s) using any of nanoparticles,borate/phosphate salt(s), pre-lithiation and coatings disclosed above(stage 210). In certain embodiments, method 200 may further compriseconfiguring the buffering zone to contain anions which are more mobilethan associate cations in the buffering zone and possibly furthercomprising configuring the buffering zone to provide a mobility gradientfor anions in the buffering zone

In certain embodiments, method 200 comprises configuring the anodematerial particles to provide flexible support for a brittle SEI (stage212), e.g., by attaching flexible polymer coating(s) to the surfacethereof. The buffering zone may be configured to comprise a polymerconfigured to support, mechanically, a solid electrolyte interphase atthe interface during expansion and contraction of the solid electrolyteinterphase.

Method 200 may comprise removing a native oxide layer from the activematerial particles (stage 214), e.g., removing any of GeO₂, SiO₂, Al₂O₃,SnO₂ at least partially, and protecting the exposed surface of theactive material particles, e.g., by disclosed coatings.

Method 200 may comprise attaching nanoparticles and/or borate/phosphatesalt(s) to active material particles (stage 220) to stabilize particlestructure, prevent or reduce agglomeration, improve lithium conductivityand/or prevent lithium metallization as disclosed above.

Method 200 may comprise lithiating the buffering zone, for example bypre-lithiating the active material particles and coating thepre-lithiated particles by conductive hydrophobic polymer(s) attachedthereto (stage 230) and/or by attaching lithium polymer(s) to the activematerial particles (stage 240).

Method 200 may comprise coating the active material particles withbonding molecules (possibly lithiated) selected to bind ionic liquidadditive in the electrolyte to the surface of the particles (stage 250).For example, in certain embodiments, method 200 may comprise forming asurface layer on the anode to bond (e.g., electrostatically and/orionically) at least some of ionic liquid additive(s) in the electrolyte,e.g., by coating the anode active material by various bonding moleculesas disclosed above and/or partly or fully pre-coating and/or coating theactive material using corresponding polymers. Method 200 may comprisecarrying out the bonding of the ionic liquid to the bonding moleculesduring at least a first charging cycle of the cell, possibly duringseveral first charging and discharging cycles. In certain embodiments,the bonding of cations and/or anions may be carried out, at leastpartially, on the active material itself, even before the first chargingcycle. The bonding of the ionic liquid to the bonding layer may beelectrostatic and/or salt-like (ionic). In certain embodiments, thebonding may be at least partly covalent.

Method 200 may comprise stabilizing the SEI of the cell through thebonded portion of the ionic liquid additive(s) to the surface layer andpossibly configuring the bonding molecules to prevent contact ofelectrolyte solvent with anode active material, e.g., through sterichindrance. Method 200 may further comprise configuring the bondingmolecules to have electron rich groups that provide mobile electriccharge on the surface of molecules layer, e.g., to provide an ionicconductivity path through the surface molecules layer.

Method 200 may comprise pre-lithiating the anode active material throughan anode material anchoring part of the bonding molecules. Method 200may comprise using anchored and interconnected conductive polymermolecules as the surface layer. Alternatively or complementarily, method200 may comprise using a thick surface layer that protrudessignificantly into the electrolyte.

Any of the examples for the bonding molecules may be at least partiallyimplemented using coating and attaching stages 220, 230, 240, and thebonding molecules may be bonded to or associated to any of the disclosedpolymers. The bonded layer of ionic liquid may replace, support orcooperate with any of the buffering zone(s) on the surface of the anodeactive material particles, provided by stages 205, 210, 212.

Method 200 may comprise carrying out any of the attaching(s) (e.g., anyof stages 220, 230, 240, 250) in a dry ball milling process or other lowenergy production processes (stage 260).

Method 200 may comprise configuring the active material particles ascomposite core-shell particles (stage 270). For example, method 200 maycomprise configuring the cores to receive and release lithium ions andthe shells to allow for core expansion and contraction while maintainingionic conductivity to the cores (stage 272), for example using activematerial particles, possibly modified, as cores, and coatings, possiblycombining brittle and flexible elements, as shells (stage 275), asdisclosed herein.

Method 200 may comprise connecting multiple cores and/or cores withshells by electronic conductive fibers (stage 280), e.g., by carbonfibers and/or nanotubes. Method 200 may further comprise formingelectric interconnections among multiple core-shell structures. Method200 may comprise connecting the cores of the core-shell particles to therespective shells by electronic conductive material. In certainembodiments, method 200 may comprise making the shells of the core-shellparticles from ionic conducting material which is an electronicinsulating material and maintaining electronic conductivity among thecores through the electronic conductive material. In certainembodiments, method 200 may comprise forming anode active material tohave cores surrounded by and connected to shells, possibly designing theshells to be ionic conducting and the connections to be electronicconducting and configuring the shells to provide space for expansion ofthe corresponding cores upon lithiation in the cores.

Method 200 may further comprise interconnecting multiple cores pershell. Method 200 may further comprise interconnecting the cores of thecore-shell particles throughout the composite anode material byconductive fibers possibly preparing an anode with conductive fibersthat reach its surface. Method 200 may comprise configuring theelectronic conductive material (e.g., conductive fibers) to form anetwork throughout the anode material to provide electron paths betweenthe core-shell particles and to enhance the electronic conductivity ofthe anode.

In certain embodiments, method 200 may comprise connecting the cores andthe respective shells by electronic conducting material(s), ionicconducting material(s), and possibly mechanical element(s) that enablecore expansion upon lithiation. In some embodiments, method 200 maycomprise forming the shells from brittle, ionic conductive materialembedded in flexible electronic conductive material. For example, theflexible electronic conductive material may comprise conductive polymersdisclosed above and the brittle ionic conductive material may compriseSEI fragments which result from cracked SEI upon expansion andcontraction of the anode material particles and/or any modifications ofthe anode material particles such as B₄C, WC, B₂O₃, P₂O₅ nanoparticlesor nanocrystals etc. which may become embedded upon expansion andcontraction of the anode material particles in any of the coatingsdisclosed above.

Method 200 may comprise preparing the anode from active materialparticles slurry and additives and preparing corresponding lithium ioncells and batteries from the anode(s), cathode(s), electrolyte(s),separator(s) and corresponding enclosure, contacts and currentcollectors, control circuits and other cell and battery elements (stage290). In certain embodiments, method 200 may comprise any of theprocessing stages of processes 105 disclosed above.

In certain embodiments, method 200 may comprise forming an alloy fromsilicon powder, carbon, and a boron-containing compound to form anactive material, and adding the active material to a matrix to form theanode material, wherein the weight percentage of the silicon is betweenabout 4 to about 35 weight % of the total weight of the anode materialand the weight percentage of the boron is between about 2 to about 20weight % of the total weight of the anode material. The active materialmay comprise carbon at a weight percentage of between about 5 to about60 weight % of the total weight of the anode material. The activematerial may comprise tungsten at a weight percentage of between about 5to about 20 weight % of the total weight of the anode material. Theactive material may further comprise carbon nanotubes (CNTs) at a weightpercentage of between about 0.05 to about 0.5 weight % of the totalweight of the anode material. The weight percentage of the silicon maybe between about 5 to about 25 weight % of the total weight of the anodematerial and the weight percentage of the boron between about 5 to about18 weight % of the total weight of the anode material. The activematerial may comprise tungsten at a weight percentage of between about 7to about 13 weight % of the total weight of the anode material. Theactive material may comprise one or more conductive materials, whereinthe weight percentage of the conductive materials may be between about0.01 to about 15 weight % of the total weight of the anode material. Theactive material may be milled to a particle size of about 20 to 100 nm.

In certain embodiments, method 200 may comprise forming an alloy fromgermanium powder, carbon, and a boron-containing compound to form anactive material, and adding the active material to a matrix to form theanode material, wherein the weight percentage of the germanium isbetween about 5 to about 80 weight % of the total weight of the anodematerial and the weight percentage of the boron is between about 2 toabout 20 weight % of the total weight of the anode material. The activematerial may comprise carbon at a weight percentage of between about 0.5to about 5 weight % of the total weight of the anode material. Theactive material may comprise tungsten at a weight percentage of betweenabout 5 to about 20 weight % of the total weight of the anode material.The active material may comprise silicon and a weight ratio of germaniumto silicon in the active material is at least 4 to 1. The weightpercentage of the germanium may be between about 60 to about 75 weight %of the total weight of the anode material and the weight percentage ofthe boron is between about 3 to about 6 weight % of the total weight ofthe anode material.

In certain embodiments, method 200 may comprise forming an alloy fromtin powder, carbon, and a boron-containing compound to form an activematerial, and adding the active material to a matrix to form the anodematerial, wherein the weight percentage of the tin is between about 5 toabout 80 weight % of the total weight of the anode material and theweight percentage of the boron is between about 2 to about 20 weight %of the total weight of the anode material. The active material maycomprise carbon at a weight percentage of between about 0.5 to about 5weight % of the total weight of the anode material. The active materialfurther comprises tungsten at a weight percentage of between about 5 toabout 20 weight % of the total weight of the anode material. The activematerial may further comprise silicon, and method 200 may compriseadding the silicon to provide a weight ratio between the tin and thesilicon is at least 4 to 1. The active material may further comprisegermanium.

In certain embodiments, method 200 may comprise forming an alloy fromaluminum powder, carbon, possibly boron and/or tungsten containingcompounds, and possibly any of Si, Ge, Sn, their alloys and/or mixtures.Method 200 may comprise at least partially removing (and/or thinning) anative alumina (oxide) layer from aluminum particles to form aluminumparticles having no more than a 1-5 nm thick alumina layer and coatingthe (at least partially exposed and/or having thinned alumina layerthereupon) aluminum particles with lithium based polymer to replace theoxide surface layer at least partially. Method 200 may comprise removingthe alumina layer at least partially through de-oxidation of aluminumparticles by mixing aluminum particles with carbon particles to form amixture and deoxidizing the aluminum particles in the mixture by heatingthe mixture in a vacuum atmosphere in a range of 10⁻³ to 10⁻⁶ mbar for60-100 hours at a temperature in a range of 600 to 750° C. to formaluminum particles at least partially exposed and/or having an aluminalayer in a thickness of no more than 5 nm. Method 200 may furthercomprise coating the de-oxidized aluminum particles with lithium basedpolymer, e.g., by ball milling the deoxidized aluminum particles withthe lithium polymer in an inert atmosphere and/or possibly applyinglithium polymers as disclosed above. In certain embodiments, method 200may comprise removing at least part of the alumina layer from aluminumparticles chemically, e.g., by immersing the aluminum particles in adilute solution of H₂SO₄ to yield the reaction Al₂O₃+3H₂SO₄ ⁻→Al₂(SO₄)₃(aq)+3H₂O, and aggressively stirring the solution with lithiumpolymer.

In certain embodiments, method 200 may comprise mixing anode materialparticles (e.g., any of Ge, Sn, Si or any other anode material disclosedherein, their alloys and combinations) with carbon particles to form amixture, deoxidizing the anode material particles in the mixture byheating the mixture in a vacuum atmosphere in a range of 10⁻³ to 10⁻⁶mbar for 60-100 hours at a temperature in a range of 150 to 350° C. toform a deoxidized mixture, adding a binder material to the deoxidizedmixture and consolidating the deoxidized mixture and binder material toform the anode. The mixing may comprise milling the anode materialparticles and carbon particles in a ball mill, possibly adding B₄Cparticles to the anode material particles and carbon particles prior tomixing and/or adding WC particles to the deoxidized mixture. Method 200may further comprise adding conductive additives to the deoxidizedmixture. The mixture may be held in a stainless steel container duringdeoxidation of the metal particles and evolved CO may be removed fromthe container during deoxidation of the anode material particles.

In certain embodiments, method 200 may comprise preparing lithiumpolymers and attaching them to the anode material particles (stage 240)as disclosed above (e.g., mixing LiOH with respective polymers and thenwith respective anode material), adjusting the process conditions tobind the polymer at least partly by the lithium to the anode material,achieving thereby also pre-lithiation (stage 230).

In certain embodiments, method 200 may comprise pre-lithiating the anodeby introducing and/or preparing anode material particles to containlithium (possibly through a prior process of pre-lithiation, possiblythrough attaching lithium polymers 240, direct lithium doping, millingprocesses, etc.) and then coating the anode material particles, whichcontain lithium ions, by a hydrophobic polymer layer (stage 230), andpreparing the anode from a slurry comprising the coated anode materialparticles, wherein the coating and the hydrophobic polymer layer areconfigured to prevent the lithium ions from chemically reacting withwater molecules in the slurry, and wherein the hydrophobic polymer layeris configured to conduct electrons and ions. In certain embodiments, thecoating may be carried out mechanically, e.g., by ball millingconfigured to maintain a structure of the anode material particles and acomposition of the hydrophobic polymer. In certain embodiments, thecoating may be carried out chemically in a suspension. The hydrophobicpolymer layer may comprise conjugated aromatic compounds and/or lithiumions which are bonded to the hydrophobic polymer.

In certain embodiments, method 200 may comprise attaching borate and/orphosphate salts (stage 220) by ball milling, under protectiveatmosphere, the anode material particles with nanoparticles comprisingB₂O₃ or other borate oxides or salts and/or P₂O₅ or other phosphateoxides or salts, and mixing the milled modified anode material particleswith conductive additives and binder to form the anode.

Experimental Data

In the following, experimental data, graphs and images are provided toexemplify some non-limiting embodiments. FIGS. 13A-13C indicate thefunctioning of buffering zone 110B, FIGS. 14A-14K are examples modifiedanode active material particles 110A, FIG. 15 illustrates borates formedin the surface of anode active material particles 110 as at leastpartial coating 120, and FIGS. 16A-B illustrate effects of in-situpolymerized polyaniline polymer coating on anode 100 according tonon-limiting embodiments of the invention

Graphs—Buffering Zone

FIGS. 13A-13C are examples for charging/discharging cycles of anodes 110with respect to lithium (half cells), according to some embodiments ofthe invention. Illustrated are cyclic voltammetry measurements at ascanning rate of 0.05 mV/s of potential windows −50 mV to 1.3V (FIG.13A), −100 mV to 1.3V (FIG. 13B) and −250 mV to 1.3V (FIG. 13C), whereinin the first two cases anode 110 maintains its operability in spite ofnegative voltages −50 mV and −100 mV applied to it, and in the thirdcases in breaks down. The repeatability of the cycles in FIG. 13Aindicates no lithium metallization process is taking place, the peak at90 mV in FIG. 13B indicates the buffering reaction Li⁺→Li^(δ+) suggestedabove (see FIG. 2C) is taking place without dendrite growth, and theprocess reversibility demonstrates the low probability of dendriteformation. It is noted that the anode breakdown illustrated in FIG. 13Cafter application of −250 mV is characteristic of prior art graphiteanodes 90 at 0V. FIGS. 13A and 13B indicate the ability of disclosedcells to overcome negative voltages applied to them and remainoperative, in stark contrast to prior art cells which are severelydamaged by negative voltages. The illustrated examples show therobustness and stability of cells prepared according to embodiments ofthe invention, and the low probability of dendrite growth on anodes 110,indicating thereby their enhanced safety. Anodes 110 in differentconfigurations may be used in disclosed embodiments, such as anodeconfigurations described herein.

Data and Images—B₄C Nanoparticles

FIGS. 14A-14F are examples for performance of anodes 100 made ofmodified anode active material particles 110A, according to someembodiments of the invention. Non-limiting examples relate to anodes 100made of modified anode material particles 110A comprising Ge anodematerial with B₄C nanoparticles 112, anodes 100 further comprising (inweight %) 6% conductive additive 130, 10% tungsten carbide (WC), 9%mixture of binder and plasticizer 102 and 75% of the active materialnano-powdered Ge—B₄C). FIG. 14A is an example for charge/dischargecurves of anode 100 in an anodic half cell (with lithium as cathode 87),with first cycle efficiency of ca. 75%, which may be increased by any ofthe pre-lithiation methods and coatings disclosed below. FIG. 14B is anexample for charge/discharge curves of anode 100 at 1^(st), 100^(th),180^(th) and 230^(th) cycles, with charging carried out at 5 C (12minutes) and discharging carried out at 0.2 C. FIG. 14C is an examplefor cycle life capacity (discharge) and cycle efficiency of anode 100and FIG. 14D is an example for the stability of anode 100, in terms ofits energy (charge) over cycling time. FIGS. 14E and 14F arecorresponding examples for full cells 150 with anodes 100, NCA cathode87, electrolyte 85 being 1M LiPF₆ in EC:DMC (1:1) with 10% FEC (ECdenoting ethylene carbonates, DMC denoting dimethyl carbonate and FECdenoting fluorinated ethylene carbonates) and separator 86 being a 12microns polypropylene separator. FIG. 14E presents charging anddischarging during the formation cycles at low C rate while FIG. 14Fdemonstrates the operation of cell 150 in fast charging at 10 C (sixminutes per charging) and discharged at low C rate, in the first 50cycles. The graph shows very small deviations and a remarkable stabilityduring the charge/discharge process.

In a non-limiting example for a preparation process, 139 g of Genanoparticles having an average particle size of 200 nm were milledtogether with 12.8 g B₄C having average particle size of 45 nm APS(aerodynamic particle size) in a planetary ball miller (a 500 mlsintered Al₂O₃ jar with approximately 200 ml of 5 mm grinding balls madeof Al₂O₃, filled with 120 ml acetone up to full volume coverage of thepowders and grinding balls). The powder was milled for 6 hours at 400rpm. Due to the hardness of the boron carbide B₄C nanoparticles 112 maybecome embedded in the surface of germanium nanoparticles 110. It isemphasized that the ball milling technique is given as an example only,and any other available method such as vapor techniques or others may beused for making a powder comprising modified anode material particles110A having nanoparticles 112 attached to anode material particles 110.

FIGS. 14G-14K are examples for modified anode active material particles110A, according to some embodiments of the invention. The illustratednon-limiting examples comprise TEM (transmission electron microscope)images of modified anode active material particles 110A prepared asindicated above (Ge—B₄C particles), and analysis data thereof. TheGe—B₄C particles (e.g., the tested powders) were made using the ballmilling technique disclosed above. The TEM micrograph of FIG. 14K showsa plurality of B₄C nanoparticles 112 (marked in circles) ofapproximately 10 nm in diameter on a surface of a Ge particle 110surrounded by carbon. FIGS. 14G, 14H and FIGS. 14I, 14J show latticestructure images of B₄C embedded in a Ge lattice (FIGS. 14H, 14J) anddiffraction profiles thereof (FIGS. 14G, 14I, respectively). From allthe TEM images it may be concluded that the B₄C particles (e.g., grainsor crystals) are at least partially embedded on the surface of the Geparticle (e.g., grain or crystal).

Image—Borates

FIG. 15 presents an example for formation of LTB in modified anodematerial particles 110A, according to some embodiments of the invention.The TEM micrograph of FIG. 15 shows the formation of B₂O₃ from Li₂B₄O₇(lithium tetra-borate salt—LTB) on the Ge active material, as describedabove. In the micrograph a clear image lattice of several LTBnanocrystals that forms a non-continuous LTB layer on a germaniumparticle.

Image and Graphs—Polyaniline Coating

FIG. 16A is an example for the surface of anode 100 produced with insitu polyaniline polymerization disclosed herein, compared to FIG. 16Bshowing an example of a cracked anode surface prepared under similarconditions without polyaniline. In the illustrated example, anodematerial particles 110 comprise Si and Sn, which were milled in desiredratio by ball milling at 300 rpm for 6 hours. 1.4 gr of milled solid wasplaced into an Erlenmeyer flask with 180 ml HCl (0.1 M) and 20 mlethanol, and sonicated for 5 minutes to disperse the powder. 400 μlaniline was added and then 0.785 gr of (NH₄)₂S₂O₈ dissolved in 20 ml HCl0.1 M. The suspension was stirred with a magnetic stirrer overnight. Thenext day, NaOH 1 M was added until the pH reached 9-10 (˜30 ml). Theproduct was washed with water and collected by centrifuge, and dried inan oven at 85° C. for 2 hours prior to use, to form anode 100 of FIG.16A. FIG. 16B is an example of an anode prepared by a similar process,without adding the aniline monomers, with the anode material particleslacking a polyaniline coating. Evidently, using polyaniline has improvedthe consistency, uniformity and stability of anode 100 significantly.In-situ polymerization of polyaniline created an even dispersion of theactive material which results in a homogeneous electrode.Advantageously, provided matrices 130 was found to overcome cracking andadhesion problems found in prior art examples, with polyaniline reducingthe amount of cracking drastically—as illustrated in FIG. 16A withrespect to prior art FIG. 16B.

FIGS. 17A and 17B are examples for improved performance of Sn:Si anodes100 produced with in situ polyaniline polymerization, according to someembodiments of the invention. FIG. 17A illustrates 1 C cycles ofcharging and discharging of half cells with anode 100 (Sn:Si withpolyaniline) with respect to an anode without polyaniline. FIG. 17Billustrates the capacity fraction in the constant current stage ofcharging of half cells with anode 100 (Sn:Si with polyaniline) withrespect to an anode without polyaniline. Both FIGS. 17A, 17B indicatehigher capacity and lower resistance of anodes 100.

Advantageously, disclosed anodes, cells and batteries mitigate oreliminate the operational risks posed by lithium ion batteries,especially as relates to intercalation of Li at the anode. Mitigated oreliminated operational risks may comprise the potential flammability ofprior art lithium ion batteries due to high reactivity of the activematerials, particularly when in contact with humidity and when batteriesare overheated and/or overcharged, which may result in thermal runaway,cell breakdown, and sometimes fire and explosion. A short circuit ordesign defect may also bring about prior art battery failure resultingin fire and safety risks. Disclosed anodes, cells and batteries mayovercome these risks, as explained above.

Advantageously, the disclosed novel anode materials with improvedlithium storage and charge/discharge characteristics overcome inherentlimitations in prior art graphite anode material in lithium-ionbatteries, such as the theoretical specific capacity and volumetriccapacity which are limited by the layer structure of the graphite.Moreover, due to the intercalation mechanism of lithium ions ingraphite, charging and discharging rates are limited, and tied tometallization of lithium, especially during fast charging followed byslow discharging. Disclosed anodes, cells and batteries may overcomethese limitations, as explained above.

Advantageously, disclosed anodes, cells and batteries provide novelanode materials and anode alloying materials and techniques that enableproductive use of new materials such as silicon, germanium, tin, leadand aluminum—utilizing their potentially high gravimetric and volumetriccapacity for lithium, while overcoming the disadvantageous discussed inthe prior art concerning the high volumetric changes duringcharging/discharging cycles which may cause low cyclability—that thesematerials suffer from. Disclosed anodes, cells and batteries mayovercome these limitations, as explained above.

In the above description, an embodiment is an example or implementationof the invention. The various appearances of “one embodiment”, “anembodiment”, “certain embodiments” or “some embodiments” do notnecessarily all refer to the same embodiments. Although various featuresof the invention may be described in the context of a single embodiment,the features may also be provided separately or in any suitablecombination. Conversely, although the invention may be described hereinin the context of separate embodiments for clarity, the invention mayalso be implemented in a single embodiment. Certain embodiments of theinvention may include features from different embodiments disclosedabove, and certain embodiments may incorporate elements from otherembodiments disclosed above. The disclosure of elements of the inventionin the context of a specific embodiment is not to be taken as limitingtheir use in the specific embodiment alone. Furthermore, it is to beunderstood that the invention can be carried out or practiced in variousways and that the invention can be implemented in certain embodimentsother than the ones outlined in the description above.

The invention is not limited to those diagrams or to the correspondingdescriptions. For example, flow need not move through each illustratedbox or state, or in exactly the same order as illustrated and described.Meanings of technical and scientific terms used herein are to becommonly understood as by one of ordinary skill in the art to which theinvention belongs, unless otherwise defined. While the invention hasbeen described with respect to a limited number of embodiments, theseshould not be construed as limitations on the scope of the invention,but rather as exemplifications of some of the preferred embodiments.Other possible variations, modifications, and applications are alsowithin the scope of the invention. Accordingly, the scope of theinvention should not be limited by what has thus far been described, butby the appended claims and their legal equivalents.

1. A method for preparing a lithium ion cell comprising: attachingnanoparticles to anode active material particles that comprise 5-80%tin, wherein the nanoparticles are at least one order of magnitudesmaller than the anode active material particles, preparing an anodefrom the anode active material particles having the attachednanoparticles, and preparing a lithium ion cell using the preparedanode.
 2. The method of claim 1, wherein the anode active materialparticles are 100-500 nm in diameter and the attached nanoparticles are10-50 nm in diameter.
 3. The method of claim 1, wherein thenanoparticles are embedded in the anode active material particles. 4.The method of claim 1, wherein the nanoparticles are made of boroncarbide and/or tungsten carbide.
 5. The method of claim 4, wherein thenanoparticles are B₄C nanoparticles present in an amount of 2-25 weight% of the anode active material particles having the attachednanoparticles.
 6. The method of claim 1, further comprising coating theanode active material particles having the attached nanoparticles with a1-10 nm thick surface layer of an amorphous carbon, graphene orgraphite.
 7. The method of claim 1, further comprising coating the anodeactive material particles having the attached nanoparticles with a 1-10nm thick surface layer of a transition metal.
 8. The method of claim 1,further comprising coating the anode active material particles havingthe attached nanoparticles with a 1-10 nm thick surface layer of alithium polymer.
 9. The method of claim 1, further comprising coatingthe anode active material particles having the attached nanoparticleswith a polymer which is conductive and/or lithiated.
 10. The method ofclaim 9, wherein the anode active material particles are 20-500 nm indiameter and the coating is 2-200 nm thick.
 11. The method of claim 1,further comprising configuring the surface layer to provide a bufferingzone that receives lithium ions from an interface of the anode activematerial particles with an electrolyte, wherein the buffering zonepartially reduces the received lithium ions, and enables the partiallyreduced lithium ions to move into an inner zone of the anode activematerial particles for lithiation therein.
 12. The method of claim 1,further comprising carrying out the attaching of the nanoparticles tothe anode active material particles by milling.
 13. The method of claim1, further comprising carrying out the anode preparation by forming aslurry with the active material particles, a solvent, and at least oneadditive selected from the group consisting of conductive particles,binder and plasticizer; and removing the solvent and consolidating theslurry to form the anode.
 14. The method of claim 1, wherein the anodeactive material particles that comprise 5-80% tin further comprise atleast one of Si, Ge, B, W, alloys thereof and mixtures thereof.
 15. Themethod of claim 14, wherein the anode active material particles thatcomprise 5-80% tin have a particle size of 100-500 nm.